diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index afcb2ce..0662457 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -10,7 +10,9 @@
   },
   "runArgs": ["--dns", "8.8.8.8", "--dns", "8.8.4.4", "--network=host", "--dns-search=."],
   "containerEnv": {
-    "HOSTALIASES": "/etc/host.aliases"
+    "HOSTALIASES": "/etc/host.aliases",
+    "GITHUB_PERSONAL_ACCESS_TOKEN": "${localEnv:GITHUB_PERSONAL_ACCESS_TOKEN}",
+    "TZ": "America/New_York"
   },
   "customizations": {
     "vscode": {
@@ -63,14 +65,10 @@
         },
         "terminal.integrated.defaultProfile.linux": "bash",
         "mcp.servers.github": {
-          "command": "docker",
+          "command": "bash",
           "args": [
-            "run",
-            "-i",
-            "--rm",
-            "--env-file",
-            "${containerWorkspaceFolder}/.devcontainer/.env",
-            "ghcr.io/github/github-mcp-server"
+            "-c",
+            "source ${containerWorkspaceFolder}/.devcontainer/library-scripts/load-env.sh && docker run -i --rm -e GITHUB_PERSONAL_ACCESS_TOKEN=\"$GITHUB_PERSONAL_ACCESS_TOKEN\" ghcr.io/github/github-mcp-server"
           ],
           "env": {}
         }
@@ -87,5 +85,8 @@
   "remoteEnv": {
     "GITHUB_PERSONAL_ACCESS_TOKEN": "${localEnv:GITHUB_PERSONAL_ACCESS_TOKEN}"
   },
-  "postStartCommand": "gh auth status || gh auth login"
+  "initializeCommand": {
+    "load-env": "echo 'Preparing environment variables for container startup'"
+  },
+  "postStartCommand": "source ${containerWorkspaceFolder}/.devcontainer/library-scripts/load-env.sh && gh auth status || gh auth login"
 }
diff --git a/README.md b/README.md
index 89a547b..7f256b6 100644
--- a/README.md
+++ b/README.md
@@ -75,4 +75,20 @@ import type { Transaction } from '@types';
 
 // ❌ DON'T use relative imports like this
 import { transactionService } from '../../../../data/db.service';
-```
\ No newline at end of file
+```
+
+### Enforcing Path Aliases with Biome.js
+
+This project uses [Biome.js](https://biomejs.dev/) for code formatting and linting. Biome enforces the use of path aliases instead of relative imports. To run Biome checks:
+
+```bash
+npm run check
+```
+
+To automatically fix issues:
+
+```bash
+npm run check -- --apply
+```
+
+The Biome configuration (in `biome.json`) includes rules for import sorting and path alias enforcement. To customize the rules, edit the `biome.json` file.
\ No newline at end of file
diff --git a/src/components/AccountSummary.astro b/src/components/AccountSummary.astro
index 8cd4b6e..fac95da 100644
--- a/src/components/AccountSummary.astro
+++ b/src/components/AccountSummary.astro
@@ -1,13 +1,19 @@
 ---
-import type { Account } from '../types';
-import { formatCurrency } from '../utils';
+import type { Account } from '@types';
+// biome-ignore lint/correctness/noUnusedImports: formatCurrency is used in the template
+import { formatCurrency } from '@utils/formatters';
 
 interface Props {
   account: Account;
 }
 const { account } = Astro.props;
 ---
+
 <div class="account-summary">
-     <h4>Account Summary</h4>
-     <p>Balance: <span id="account-balance">{formatCurrency(account.balance)}</span></p>
-</div>
\ No newline at end of file
+  <h4>Account Summary</h4>
+  <p>
+    Balance: <span id="account-balance"
+      >{formatCurrency(Number(account.balance))}</span
+    >
+  </p>
+</div>
diff --git a/src/components/AccountSummary.tsx b/src/components/AccountSummary.tsx
index f96fac9..3664471 100644
--- a/src/components/AccountSummary.tsx
+++ b/src/components/AccountSummary.tsx
@@ -1,8 +1,8 @@
 import { useStore } from '@nanostores/react';
+import { currentAccountId as currentAccountIdStore, refreshKey } from '@stores/transactionStore';
+import type { Account } from '@types';
+import { formatCurrency } from '@utils/formatters';
 import { useEffect, useState } from 'react';
-import { currentAccountId as currentAccountIdStore, refreshKey } from '../stores/transactionStore';
-import type { Account } from '../types';
-import { formatCurrency } from '../utils';
 
 export default function AccountSummary() {
   const currentAccountId = useStore(currentAccountIdStore);
@@ -11,6 +11,7 @@ export default function AccountSummary() {
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  // biome-ignore lint/correctness/useExhaustiveDependencies: refreshCounter is needed to trigger refresh on transaction changes
   useEffect(() => {
     if (!currentAccountId) {
       setAccount(null);
@@ -51,17 +52,17 @@ export default function AccountSummary() {
   } else if (error) {
     balanceContent = <span className="error-message">Error: {error}</span>;
   } else if (account) {
-    balanceContent = formatCurrency(account.balance);
+    balanceContent = formatCurrency(Number(account.balance));
   } else {
     balanceContent = 'N/A';
   }
 
   return (
     <div className="account-summary">
-      <h4>Account Summary</h4>
-      <p>
-        Balance: <span id="account-balance">{balanceContent}</span>
-      </p>
+      <div className="account-summary-header">
+        <h4>Account Summary</h4>
+        <div id="account-balance">{balanceContent}</div>
+      </div>
     </div>
   );
 }
diff --git a/src/components/AddTransactionForm.tsx b/src/components/AddTransactionForm.tsx
index c4e7e98..dc54f78 100644
--- a/src/components/AddTransactionForm.tsx
+++ b/src/components/AddTransactionForm.tsx
@@ -1,13 +1,16 @@
 import { useStore } from '@nanostores/react';
-import React, { useEffect, useState } from 'react';
+import * as Form from '@radix-ui/react-form';
+import * as Toast from '@radix-ui/react-toast';
 import {
   cancelEditingTransaction,
   currentAccountId,
   loadTransactionsForAccount,
   transactionSaved,
   transactionToEdit,
-  triggerRefresh,
-} from '../stores/transactionStore';
+} from '@stores/transactionStore';
+import type { Transaction } from '@types';
+import type React from 'react';
+import { useEffect, useState } from 'react';
 
 export default function AddTransactionForm() {
   const accountId = useStore(currentAccountId);
@@ -18,10 +21,10 @@ export default function AddTransactionForm() {
   const [description, setDescription] = useState('');
   const [amount, setAmount] = useState('');
   const [category, setCategory] = useState('');
-  const [type, setType] = useState('WITHDRAWAL');
   const [isSubmitting, setIsSubmitting] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const [successMessage, setSuccessMessage] = useState<string | null>(null);
+  const [toastOpen, setToastOpen] = useState(false);
 
   // Set initial date only on client-side after component mounts
   useEffect(() => {
@@ -30,14 +33,15 @@ export default function AddTransactionForm() {
       const today = new Date();
       setDate(today.toISOString().split('T')[0]);
     }
-  }, []);
+  }, [date]);
 
   // Reset form when accountId changes or when switching from edit to add mode
+  // biome-ignore lint/correctness/useExhaustiveDependencies: accountId is needed to trigger form reset when account changes
   useEffect(() => {
     if (!editingTransaction) {
       resetForm();
     }
-  }, [accountId, editingTransaction === null]);
+  }, [accountId, editingTransaction]); // accountId is intentionally included for form reset on account change
 
   // Populate form when editing a transaction
   useEffect(() => {
@@ -60,11 +64,11 @@ export default function AddTransactionForm() {
 
       setDate(dateStr);
       setDescription(editingTransaction.description);
-      setAmount(String(Math.abs(editingTransaction.amount)));
+      // Set amount directly as positive or negative value
+      setAmount(String(editingTransaction.amount));
       setCategory(editingTransaction.category || '');
-      setType(editingTransaction.amount < 0 ? 'WITHDRAWAL' : 'DEPOSIT');
     }
-  }, [editingTransaction]);
+  }, [editingTransaction]); // Add editingTransaction to dependencies
 
   const resetForm = () => {
     // Get today's date in YYYY-MM-DD format for the date input
@@ -73,21 +77,86 @@ export default function AddTransactionForm() {
     setDescription('');
     setAmount('');
     setCategory('');
-    setType('WITHDRAWAL');
     setError(null);
     setSuccessMessage(null);
   };
 
+  const validateFormData = () => {
+    if (!editingTransaction && !accountId) {
+      setError('No account selected. Please select an account before adding a transaction.');
+      return false;
+    }
+    if (!date || !description || !amount) {
+      setError('Date, description, and amount are required fields.');
+      return false;
+    }
+    return true;
+  };
+
+  const prepareTransactionData = () => {
+    const isEditing = !!editingTransaction;
+    return {
+      transaction: {
+        accountId: editingTransaction ? editingTransaction.accountId : accountId,
+        date,
+        description,
+        amount: Number.parseFloat(amount),
+        category: category || undefined,
+      },
+      url: isEditing ? `/api/transactions/${editingTransaction.id}` : '/api/transactions',
+      method: isEditing ? 'PUT' : 'POST',
+    };
+  };
+
+  const saveTransaction = async (url: string, method: string, data: Omit<Transaction, 'id'>) => {
+    const response = await fetch(url, {
+      method,
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(data),
+    });
+
+    if (!response.ok) {
+      const errorData = await response.json();
+      const isEditing = !!editingTransaction;
+      throw new Error(errorData.error || `Failed to ${isEditing ? 'update' : 'add'} transaction`);
+    }
+
+    return response.json() as Promise<Transaction>;
+  };
+
+  const handleSuccess = async (savedTransaction: Transaction) => {
+    const isEditing = !!editingTransaction;
+    setSuccessMessage(`Transaction ${isEditing ? 'updated' : 'added'} successfully!`);
+    setToastOpen(true);
+    resetForm();
+
+    if (isEditing) {
+      cancelEditingTransaction();
+    }
+
+    transactionSaved(savedTransaction);
+
+    // Reload transactions for affected accounts
+    const accountToReload = isEditing ? editingTransaction.accountId : accountId;
+    if (accountToReload) {
+      await loadTransactionsForAccount(accountToReload);
+    }
+    if (isEditing && accountId && editingTransaction.accountId !== accountId) {
+      await loadTransactionsForAccount(accountId);
+    }
+  };
+
+  const handleError = (err: unknown) => {
+    const errorMessage = err instanceof Error ? err.message : 'An unknown error occurred.';
+    setError(errorMessage);
+    const isEditing = !!editingTransaction;
+    console.error(`Transaction ${isEditing ? 'update' : 'submission'} error:`, err);
+  };
+
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
 
-    if (!accountId) {
-      setError('No account selected');
-      return;
-    }
-
-    if (!date || !description || !amount) {
-      setError('Date, description and amount are required');
+    if (!validateFormData()) {
       return;
     }
 
@@ -95,76 +164,12 @@ export default function AddTransactionForm() {
     setError(null);
     setSuccessMessage(null);
 
-    // Calculate final amount based on type
-    const finalAmount = type === 'DEPOSIT' ? Math.abs(Number(amount)) : -Math.abs(Number(amount));
-
     try {
-      let response;
-
-      if (editingTransaction) {
-        // Update existing transaction
-        response = await fetch(`/api/transactions/${editingTransaction.id}`, {
-          method: 'PUT',
-          headers: {
-            'Content-Type': 'application/json',
-          },
-          body: JSON.stringify({
-            accountId,
-            date,
-            description,
-            amount: finalAmount,
-            category: category || undefined,
-            type,
-          }),
-        });
-      } else {
-        // Create new transaction
-        response = await fetch('/api/transactions', {
-          method: 'POST',
-          headers: {
-            'Content-Type': 'application/json',
-          },
-          body: JSON.stringify({
-            accountId,
-            date,
-            description,
-            amount: finalAmount,
-            category: category || undefined,
-            type,
-          }),
-        });
-      }
-
-      if (!response.ok) {
-        const errorData = await response.json();
-        throw new Error(errorData.error || 'Transaction operation failed');
-      }
-
-      const savedTransaction = await response.json();
-
-      // Handle success
-      setSuccessMessage(
-        editingTransaction
-          ? 'Transaction updated successfully!'
-          : 'Transaction added successfully!',
-      );
-
-      // Reset form
-      resetForm();
-
-      // Clear editing state
-      if (editingTransaction) {
-        cancelEditingTransaction();
-      }
-
-      // Notify about saved transaction
-      transactionSaved(savedTransaction);
-
-      // Reload transactions to ensure the list is up to date
-      await loadTransactionsForAccount(accountId);
+      const { url, method, transaction } = prepareTransactionData();
+      const savedTransaction = await saveTransaction(url, method, transaction);
+      await handleSuccess(savedTransaction);
     } catch (err) {
-      setError(err instanceof Error ? err.message : 'An unknown error occurred');
-      console.error('Transaction error:', err);
+      handleError(err);
     } finally {
       setIsSubmitting(false);
     }
@@ -181,89 +186,138 @@ export default function AddTransactionForm() {
     <div className="transaction-form-container">
       <h3>{editingTransaction ? 'Edit Transaction' : 'Add Transaction'}</h3>
 
-      {successMessage && <div className="success-message">{successMessage}</div>}
-
-      {error && <div className="error-message">{error}</div>}
-
-      <form onSubmit={handleSubmit}>
-        <div className="form-group">
-          <label htmlFor="txn-date">Date:</label>
-          <input
-            type="date"
-            id="txn-date"
-            value={date}
-            onChange={(e) => setDate(e.target.value)}
-            disabled={isSubmitting}
-            required
-          />
-        </div>
-
-        <div className="form-group">
-          <label htmlFor="txn-description">Description:</label>
-          <input
-            type="text"
-            id="txn-description"
-            value={description}
-            onChange={(e) => setDescription(e.target.value)}
-            disabled={isSubmitting}
-            placeholder="e.g., Grocery store"
-            required
-          />
-        </div>
-
-        <div className="form-group amount-group">
-          <label htmlFor="txn-amount">Amount:</label>
-          <div className="amount-input-group">
-            <select value={type} onChange={(e) => setType(e.target.value)} disabled={isSubmitting}>
-              <option value="WITHDRAWAL">-</option>
-              <option value="DEPOSIT">+</option>
-            </select>
-            <span className="currency-symbol">$</span>
-            <input
-              type="number"
-              id="txn-amount"
-              value={amount}
-              onChange={(e) => setAmount(e.target.value)}
-              disabled={isSubmitting}
-              step="0.01"
-              min="0"
-              placeholder="0.00"
-              required
-            />
+      <Toast.Provider swipeDirection="right">
+        {error && (
+          <div className="error-message" role="alert">
+            {error}
           </div>
-        </div>
+        )}
 
-        <div className="form-group">
-          <label htmlFor="txn-category">Category (optional):</label>
-          <input
-            type="text"
-            id="txn-category"
-            value={category}
-            onChange={(e) => setCategory(e.target.value)}
-            disabled={isSubmitting}
-            placeholder="e.g., Food, Bills, etc."
-          />
-        </div>
+        <Form.Root onSubmit={handleSubmit} className="form-root">
+          <Form.Field className="form-field" name="date">
+            <div
+              style={{ display: 'flex', alignItems: 'baseline', justifyContent: 'space-between' }}
+            >
+              <Form.Label className="form-label">Date</Form.Label>
+              <Form.Message className="form-message" match="valueMissing">
+                Please enter a date
+              </Form.Message>
+            </div>
+            <Form.Control asChild>
+              <input
+                type="date"
+                className="form-input"
+                value={date}
+                onChange={(e) => setDate(e.target.value)}
+                disabled={isSubmitting}
+                required
+              />
+            </Form.Control>
+          </Form.Field>
 
-        <div className="form-actions">
-          <button
-            type="button"
-            onClick={handleCancel}
-            disabled={isSubmitting}
-            className="cancel-btn"
-          >
-            Cancel
-          </button>
-          <button
-            type="submit"
-            // Allow submitting if we're editing a transaction, even if no account is currently selected
-            disabled={isSubmitting || (!editingTransaction && !accountId)}
-            className="submit-btn"
-          >
-            {isSubmitting ? 'Processing...' : editingTransaction ? 'Update' : 'Add'}
-          </button>
-        </div>
-      </form>
+          <Form.Field className="form-field" name="description">
+            <div
+              style={{ display: 'flex', alignItems: 'baseline', justifyContent: 'space-between' }}
+            >
+              <Form.Label className="form-label">Description</Form.Label>
+              <Form.Message className="form-message" match="valueMissing">
+                Please enter a description
+              </Form.Message>
+            </div>
+            <Form.Control asChild>
+              <input
+                type="text"
+                className="form-input"
+                value={description}
+                onChange={(e) => setDescription(e.target.value)}
+                disabled={isSubmitting}
+                placeholder="e.g., Grocery store"
+                required
+              />
+            </Form.Control>
+          </Form.Field>
+
+          <Form.Field className="form-field" name="amount">
+            <div
+              style={{ display: 'flex', alignItems: 'baseline', justifyContent: 'space-between' }}
+            >
+              <Form.Label className="form-label">Amount (negative for expenses)</Form.Label>
+              <Form.Message className="form-message" match="valueMissing">
+                Please enter an amount
+              </Form.Message>
+            </div>
+            <div className="amount-input-wrapper">
+              <span className="currency-symbol">$</span>
+              <Form.Control asChild>
+                <input
+                  type="number"
+                  className="form-input amount-input"
+                  value={amount}
+                  onChange={(e) => setAmount(e.target.value)}
+                  disabled={isSubmitting}
+                  step="0.01"
+                  placeholder="0.00 (negative for expenses)"
+                  required
+                />
+              </Form.Control>
+            </div>
+          </Form.Field>
+
+          <Form.Field className="form-field" name="category">
+            <div
+              style={{ display: 'flex', alignItems: 'baseline', justifyContent: 'space-between' }}
+            >
+              <Form.Label className="form-label">Category (optional)</Form.Label>
+            </div>
+            <Form.Control asChild>
+              <input
+                type="text"
+                className="form-input"
+                value={category}
+                onChange={(e) => setCategory(e.target.value)}
+                disabled={isSubmitting}
+                placeholder="e.g., Food, Bills, etc."
+              />
+            </Form.Control>
+          </Form.Field>
+
+          <div className="form-actions">
+            <button
+              type="button"
+              onClick={handleCancel}
+              disabled={isSubmitting}
+              className="cancel-btn"
+            >
+              Cancel
+            </button>
+            <Form.Submit asChild>
+              <button
+                type="submit"
+                // Allow submitting if we're editing a transaction, even if no account is currently selected
+                disabled={isSubmitting || (!editingTransaction && !accountId)}
+                className="submit-btn"
+              >
+                {isSubmitting ? 'Processing...' : editingTransaction ? 'Update' : 'Add'}
+              </button>
+            </Form.Submit>
+          </div>
+        </Form.Root>
+
+        <Toast.Root
+          className="toast-root"
+          open={toastOpen}
+          onOpenChange={setToastOpen}
+          duration={3000}
+        >
+          <Toast.Title className="toast-title">{successMessage}</Toast.Title>
+          <Toast.Action className="toast-action" asChild altText="Close">
+            <button type="button" className="toast-close-button">
+              ✕
+            </button>
+          </Toast.Action>
+        </Toast.Root>
+        <Toast.Viewport className="toast-viewport" />
+      </Toast.Provider>
     </div>
   );
 }
diff --git a/src/components/MainContent.astro b/src/components/MainContent.astro
index ddc8114..c9d20f8 100644
--- a/src/components/MainContent.astro
+++ b/src/components/MainContent.astro
@@ -1,6 +1,5 @@
 ---
-import type { Account } from '../types';
-import TransactionTable from './TransactionTable.tsx';
+import type { Account } from '@types';
 
 interface Props {
   account: Account;
@@ -8,9 +7,13 @@ interface Props {
 
 const { account } = Astro.props;
 ---
+
 <main class="main-content">
-    <header class="main-header">
-         <h1>Transactions for <span id="current-account-name">{account.name} (***{account.accountNumber.slice(-3)})</span></h1>
-    </header>
-    <TransactionTable client:load />
-</main>
\ No newline at end of file
+  <header class="main-header">
+    <h1>
+      Transactions for <span id="current-account-name"
+        >{account.name} (***{account.accountNumber.slice(-3)})</span>
+    </h1>
+  </header>
+  <TransactionTable client:load />
+</main>
diff --git a/src/components/Sidebar.astro b/src/components/Sidebar.astro
index f6ebe1c..2dc8fd3 100644
--- a/src/components/Sidebar.astro
+++ b/src/components/Sidebar.astro
@@ -1,11 +1,9 @@
 ---
-import type { Account } from "../types";
-import AccountSummary from "./AccountSummary.tsx"; // Import the React component instead of the Astro one
-import AddTransactionForm from "./AddTransactionForm.tsx";
+import type { Account } from '@types';
 
 interface Props {
-    accounts: Account[];
-    initialAccount: Account;
+  accounts: Account[];
+  initialAccount: Account;
 }
 
 const { accounts, initialAccount } = Astro.props;
@@ -14,18 +12,10 @@ const { accounts, initialAccount } = Astro.props;
 <aside class="sidebar">
     <div class="sidebar-header">
         <h2>My finances</h2>
-        {/* Add button to toggle form visibility */}
-        <button
-            id="toggle-add-txn-btn"
-            aria-expanded="false"
-            aria-controls="add-transaction-section"
-        >
-            + New Txn
-        </button>
     </div>
     <nav class="account-nav">
         <h3>Accounts</h3>
-        <select id="account-select" name="account">
+        <select id="account-select" name="account" class="form-input">
             {
                 accounts.map((account) => (
                     <option
@@ -39,43 +29,176 @@ const { accounts, initialAccount } = Astro.props;
         </select>
     </nav>
 
-    {/* Use the React AccountSummary component, remove account prop */}
-    <AccountSummary client:load />
-
-    {/* Section to contain the React form, initially hidden */}
-    <section id="add-transaction-section" class="collapsible collapsed">
-        {
-            /*
-            Use the React component here.
-            It now gets its state (currentAccountId, transactionToEdit)
-            directly from the Nano Store.
-         */
-        }
-        <AddTransactionForm client:load />
+    <!-- Add Transaction Section with Toggle - Moved up to be right after account dropdown -->
+    <section id="add-transaction-section" class="add-transaction-section">
+        <button
+            type="button"
+            class="toggle-form-btn"
+            id="toggle-add-txn-btn"
+            aria-controls="add-transaction-form"
+            aria-expanded="false"
+        >
+            Add Transaction
+        </button>
+        <div id="add-transaction-form" class="collapsible-form collapsed">
+            <AddTransactionForm client:load />
+        </div>
     </section>
+
+    <!-- Account Summary Section - Always visible -->
+    <div class="account-summary-section" id="account-summary-section">
+        <AccountSummary client:load />
+    </div>
 </aside>
 
-{/* Keep the script for toggling visibility for now */}
-<script>
-    const toggleButton = document.getElementById("toggle-add-txn-btn");
-    const formSection = document.getElementById("add-transaction-section");
+<!-- Toggle button for sidebar on mobile -->
+<button
+    type="button"
+    class="sidebar-toggle"
+    id="sidebar-toggle"
+    aria-controls="sidebar-content"
+    aria-expanded="true"
+>
+    <span>Toggle sidebar</span>
+    <span class="sidebar-toggle-icon">▲</span>
+</button>
 
-    if (toggleButton && formSection) {
-        toggleButton.addEventListener("click", () => {
-            const isExpanded =
-                toggleButton.getAttribute("aria-expanded") === "true";
-            toggleButton.setAttribute("aria-expanded", String(!isExpanded));
-            formSection.classList.toggle("collapsed");
-            formSection.classList.toggle("expanded");
-            // Optional: Focus first field when expanding
-            if (!isExpanded) {
-                // Cast the result to HTMLElement before calling focus
-                (
-                    formSection.querySelector(
-                        "input, select, textarea",
-                    ) as HTMLElement
-                )?.focus();
-            }
-        });
-    }
+<script>
+    // Add Transaction form toggle
+    const toggleAddTxnBtn = document.getElementById("toggle-add-txn-btn");
+    const addTransactionForm = document.getElementById("add-transaction-form");
+
+    toggleAddTxnBtn?.addEventListener("click", () => {
+        const isExpanded =
+            toggleAddTxnBtn.getAttribute("aria-expanded") === "true";
+        toggleAddTxnBtn.setAttribute(
+            "aria-expanded",
+            isExpanded ? "false" : "true",
+        );
+
+        if (isExpanded) {
+            addTransactionForm?.classList.add("collapsed");
+        } else {
+            addTransactionForm?.classList.remove("collapsed");
+        }
+    });
+
+    // Sidebar toggle for mobile
+    const sidebarToggleBtn = document.getElementById("sidebar-toggle");
+    const sidebar = document.querySelector(".sidebar");
+
+    sidebarToggleBtn?.addEventListener("click", () => {
+        const isExpanded =
+            sidebarToggleBtn.getAttribute("aria-expanded") === "true";
+        sidebarToggleBtn.setAttribute(
+            "aria-expanded",
+            isExpanded ? "false" : "true",
+        );
+
+        if (isExpanded) {
+            sidebar?.classList.add("sidebar-collapsed");
+        } else {
+            sidebar?.classList.remove("sidebar-collapsed");
+        }
+    });
+
+    // Check if we're on mobile and collapse sidebar by default
+    const checkMobile = () => {
+        const isMobile = window.innerWidth < 1024;
+
+        if (isMobile && sidebar && sidebarToggleBtn) {
+            // Start with sidebar collapsed on mobile
+            sidebar.classList.add("sidebar-collapsed");
+            sidebarToggleBtn.setAttribute("aria-expanded", "false");
+        } else if (sidebar && sidebarToggleBtn) {
+            sidebar.classList.remove("sidebar-collapsed");
+            sidebarToggleBtn.setAttribute("aria-expanded", "true");
+        }
+    };
+
+    // Check on load and window resize
+    window.addEventListener("load", checkMobile);
+    window.addEventListener("resize", checkMobile);
 </script>
+
+<style>
+    .sidebar {
+        padding: 20px;
+        background-color: #f9fafb;
+        border-right: 1px solid #e5e7eb;
+        height: 100%;
+        overflow-y: auto;
+    }
+
+    .sidebar-collapsed {
+        display: none;
+    }
+
+    .sidebar-header {
+        display: flex;
+        align-items: center;
+        justify-content: space-between;
+        margin-bottom: 24px;
+    }
+
+    .account-nav {
+        margin-bottom: 15px;
+    }
+
+    .account-nav h3 {
+        margin-bottom: 8px;
+        font-size: 16px;
+    }
+
+    /* Ensure account summary is always visible */
+    .account-summary-section {
+        margin-bottom: 15px;
+        padding-bottom: 5px;
+    }
+
+    .add-transaction-section {
+        margin-bottom: 15px;
+    }
+
+    .add-transaction-section .toggle-form-btn {
+        display: block;
+        width: 100%;
+        margin-bottom: 0;
+    }
+
+    .collapsible-form.collapsed {
+        display: none;
+    }
+
+    .sidebar-toggle {
+        display: none;
+        position: fixed;
+        bottom: 20px;
+        right: 20px;
+        background-color: #f9fafb;
+        border: 1px solid #e5e7eb;
+        padding: 10px;
+        cursor: pointer;
+        z-index: 100;
+        width: auto;
+        min-width: 140px;
+        text-align: center;
+        box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
+        border-radius: 4px;
+    }
+
+    .sidebar-toggle span {
+        pointer-events: none;
+    }
+
+    .sidebar-toggle-icon {
+        margin-left: 8px;
+        pointer-events: none;
+    }
+
+    @media (max-width: 1024px) {
+        .sidebar-toggle {
+            display: block;
+        }
+    }
+</style>
diff --git a/src/components/TransactionTable.astro b/src/components/TransactionTable.astro
index 6968582..5f516f4 100644
--- a/src/components/TransactionTable.astro
+++ b/src/components/TransactionTable.astro
@@ -1,6 +1,5 @@
 ---
-import type { Transaction } from '../types';
-import { formatCurrency, formatDate } from '../utils';
+import type { Transaction } from '@types';
 
 interface Props {
   transactions: Transaction[];
@@ -21,6 +20,7 @@ const sortedTransactions = [...transactions].sort(
 // - Add transaction details expansion/collapse
 // - Consider adding bulk actions (delete, categorize)
 ---
+
 <section class="transaction-list" id="transaction-section">
     <table id="transaction-table">
         <thead>
@@ -32,24 +32,45 @@ const sortedTransactions = [...transactions].sort(
             </tr>
         </thead>
         <tbody id="transaction-table-body">
-            {sortedTransactions.map(txn => (
-                <tr data-txn-id={txn.id}>
-                    <td>{formatDate(txn.date)}</td>
-                    <td>{txn.description}</td>
-                    <td class={`amount-col ${txn.amount >= 0 ? 'amount-positive' : 'amount-negative'}`}>
-                        {formatCurrency(txn.amount)}
-                    </td>
-                    <td>
-                        <button class="action-btn edit-btn" title="Edit transaction">Edit</button>
-                        <button class="action-btn delete-btn" title="Delete transaction">Delete</button>
-                    </td>
-                </tr>
-            ))}
-            {sortedTransactions.length === 0 && (
-                <tr>
-                    <td colspan="4" style="text-align: center; font-style: italic; color: #777;">No transactions found for this account.</td>
-                </tr>
-            )}
+            {
+                sortedTransactions.map((txn) => (
+                    <tr data-txn-id={txn.id}>
+                        <td>{formatDate(txn.date)}</td>
+                        <td>{txn.description}</td>
+                        <td
+                            class={`amount-col ${Number(txn.amount) >= 0 ? "amount-positive" : "amount-negative"}`}
+                        >
+                            {formatCurrency(Number(txn.amount))}
+                        </td>
+                        <td>
+                            <button
+                                class="action-btn edit-btn"
+                                title="Edit transaction"
+                            >
+                                Edit
+                            </button>
+                            <button
+                                class="action-btn delete-btn"
+                                title="Delete transaction"
+                            >
+                                Delete
+                            </button>
+                        </td>
+                    </tr>
+                ))
+            }
+            {
+                sortedTransactions.length === 0 && (
+                    <tr>
+                        <td
+                            colspan="4"
+                            style="text-align: center; font-style: italic; color: #777;"
+                        >
+                            No transactions found for this account.
+                        </td>
+                    </tr>
+                )
+            }
         </tbody>
     </table>
-</section>
\ No newline at end of file
+</section>
diff --git a/src/components/TransactionTable.tsx b/src/components/TransactionTable.tsx
index 915c83e..f14e65d 100644
--- a/src/components/TransactionTable.tsx
+++ b/src/components/TransactionTable.tsx
@@ -1,15 +1,15 @@
 import { useStore } from '@nanostores/react';
-import React, { useState, useEffect, useCallback } from 'react';
 import {
   currentAccountId as currentAccountIdStore,
   currentTransactions as currentTransactionsStore,
+  loadTransactionsForAccount,
   refreshKey,
   startEditingTransaction,
   triggerRefresh,
-  loadTransactionsForAccount,
-} from '../stores/transactionStore';
-import type { Transaction } from '../types';
-import { formatCurrency, formatDate } from '../utils';
+} from '@stores/transactionStore';
+import type { Transaction } from '@types';
+import { formatCurrency, formatDate } from '@utils/formatters';
+import { useCallback, useEffect, useState } from 'react';
 
 export default function TransactionTable() {
   const currentAccountId = useStore(currentAccountIdStore);
@@ -18,6 +18,7 @@ export default function TransactionTable() {
 
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
+  const [isMobileView, setIsMobileView] = useState(false);
 
   // Fetch transactions when account ID changes or refresh is triggered
   const fetchTransactions = useCallback(async () => {
@@ -42,11 +43,27 @@ export default function TransactionTable() {
     }
   }, [currentAccountId]);
 
-  // Effect for loading transactions when account changes or refresh is triggered
+  // biome-ignore lint/correctness/useExhaustiveDependencies: refreshCounter is needed to trigger transaction reload when data changes
   useEffect(() => {
     fetchTransactions();
   }, [fetchTransactions, refreshCounter]);
 
+  // Check for mobile view on mount and resize
+  useEffect(() => {
+    const checkViewport = () => {
+      setIsMobileView(window.innerWidth < 640);
+    };
+
+    // Check on mount
+    checkViewport();
+
+    // Add resize listener
+    window.addEventListener('resize', checkViewport);
+
+    // Clean up
+    return () => window.removeEventListener('resize', checkViewport);
+  }, []);
+
   // Safe sort function that handles invalid dates gracefully
   const safeSort = (transactions: Transaction[]) => {
     if (!Array.isArray(transactions)) {
@@ -156,32 +173,84 @@ export default function TransactionTable() {
     sortedTransactions.map((txn) => (
       <tr key={txn.id} data-txn-id={txn.id}>
         <td>{formatDate(txn.date)}</td>
-        <td>{txn.description || 'No description'}</td>
-        <td className={`amount-col ${txn.amount >= 0 ? 'amount-positive' : 'amount-negative'}`}>
-          {formatCurrency(txn.amount)}
+        <td className="description-col">{txn.description || 'No description'}</td>
+        <td
+          className={`amount-col ${Number(txn.amount) >= 0 ? 'amount-positive' : 'amount-negative'}`}
+        >
+          {formatCurrency(Number(txn.amount))}
         </td>
-        <td>{txn.category || 'Uncategorized'}</td>
-        <td>
+        <td className="category-col">{txn.category || 'Uncategorized'}</td>
+        <td className="actions-col">
           <button
             type="button"
             className="action-btn edit-btn"
             title="Edit transaction"
             onClick={() => handleEdit(txn)}
+            aria-label="Edit transaction"
           >
-            Edit
+            <i className="fa-solid fa-pen-to-square button-icon" aria-hidden="true" tabIndex={-1} />
+            <span className="button-text">Edit</span>
           </button>
           <button
             type="button"
             className="action-btn delete-btn"
             title="Delete transaction"
             onClick={() => handleDelete(txn.id)}
+            aria-label="Delete transaction"
           >
-            Delete
+            <i className="fa-solid fa-trash-can button-icon" aria-hidden="true" tabIndex={-1} />
+            <span className="button-text">Delete</span>
           </button>
         </td>
       </tr>
     ));
 
+  // Mobile view - card-based rendering for transactions
+  const renderMobileCards = () =>
+    sortedTransactions.map((txn) => (
+      <div key={txn.id} className="transaction-card" data-txn-id={txn.id}>
+        <div className="transaction-card-header">
+          <div className="transaction-card-date">{formatDate(txn.date)}</div>
+          <div
+            className={`transaction-card-amount ${Number(txn.amount) >= 0 ? 'amount-positive' : 'amount-negative'}`}
+          >
+            {formatCurrency(Number(txn.amount))}
+          </div>
+        </div>
+        <div className="transaction-card-description">{txn.description || 'No description'}</div>
+        <div className="transaction-card-footer">
+          <div className="transaction-card-category">
+            <span className="transaction-card-label">Category:</span>{' '}
+            {txn.category || 'Uncategorized'}
+          </div>
+          <div className="transaction-card-actions">
+            <button
+              type="button"
+              className="action-btn edit-btn"
+              title="Edit transaction"
+              onClick={() => handleEdit(txn)}
+              aria-label="Edit transaction"
+            >
+              <i
+                className="fa-solid fa-pen-to-square button-icon"
+                aria-hidden="true"
+                tabIndex={-1}
+              />
+            </button>
+            <button
+              type="button"
+              className="action-btn delete-btn"
+              title="Delete transaction"
+              onClick={() => handleDelete(txn.id)}
+              aria-label="Delete transaction"
+            >
+              <i className="fa-solid fa-trash-can button-icon" aria-hidden="true" tabIndex={-1} />
+            </button>
+          </div>
+        </div>
+      </div>
+    ));
+
   return (
     <div id="transaction-section" className={isLoading ? 'loading' : ''}>
       {error && (
@@ -189,24 +258,41 @@ export default function TransactionTable() {
           Error loading transactions: {error}
         </div>
       )}
-      <table className="transaction-table">
-        <thead>
-          <tr>
-            <th>Date</th>
-            <th>Description</th>
-            <th className="amount-col">Amount</th>
-            <th>Category</th>
-            <th>Actions</th>
-          </tr>
-        </thead>
-        <tbody id="transaction-table-body">
-          {isLoading
-            ? renderLoading()
-            : sortedTransactions.length === 0
-              ? renderEmpty()
-              : renderRows()}
-        </tbody>
-      </table>
+
+      {isMobileView ? (
+        // Mobile view: card-based layout
+        <div className="transaction-cards">
+          {isLoading ? (
+            <div className="loading-message">Loading transactions...</div>
+          ) : sortedTransactions.length === 0 ? (
+            <div className="empty-message">No transactions found for this account.</div>
+          ) : (
+            renderMobileCards()
+          )}
+        </div>
+      ) : (
+        // Desktop view: table layout
+        <div className="transaction-table-container">
+          <table className="transaction-table">
+            <thead>
+              <tr>
+                <th>Date</th>
+                <th>Description</th>
+                <th className="amount-col">Amount</th>
+                <th>Category</th>
+                <th>Actions</th>
+              </tr>
+            </thead>
+            <tbody id="transaction-table-body">
+              {isLoading
+                ? renderLoading()
+                : sortedTransactions.length === 0
+                  ? renderEmpty()
+                  : renderRows()}
+            </tbody>
+          </table>
+        </div>
+      )}
     </div>
   );
 }
diff --git a/src/data/db.service.ts b/src/data/db.service.ts
index 8f3c8dd..4f971ec 100644
--- a/src/data/db.service.ts
+++ b/src/data/db.service.ts
@@ -1,5 +1,3 @@
-import type { Prisma, PrismaClient } from '@prisma/client';
-import { Decimal } from '@prisma/client/runtime/library';
 import type { Account, Transaction } from '@types';
 import { prisma } from './prisma';
 
diff --git a/src/layouts/BaseLayout.astro b/src/layouts/BaseLayout.astro
index fc23a11..e6d1e2b 100644
--- a/src/layouts/BaseLayout.astro
+++ b/src/layouts/BaseLayout.astro
@@ -14,6 +14,7 @@ interface Props {
 
 const { title } = Astro.props;
 ---
+
 <!doctype html>
 <html lang="en">
 	<head>
@@ -23,9 +24,16 @@ const { title } = Astro.props;
 		<link rel="icon" type="image/svg+xml" href="/favicon.svg" />
 		<meta name="generator" content={Astro.generator} />
 		<title>{title}</title>
-        <link rel="stylesheet" href="/src/styles/global.css">
+		<link rel="stylesheet" href="/src/styles/radix-ui.css" />
+		<link
+			rel="stylesheet"
+			href="/node_modules/@fortawesome/fontawesome-free/css/all.min.css"
+		/>
+		<link rel="stylesheet" href="/src/styles/global.css" />
 	</head>
 	<body>
-		<slot />
+		<main>
+			<slot />
+		</main>
 	</body>
-</html>
\ No newline at end of file
+</html>
diff --git a/src/pages/api/transactions/[id]/index.ts b/src/pages/api/transactions/[id]/index.ts
index a7de26e..a06dd05 100644
--- a/src/pages/api/transactions/[id]/index.ts
+++ b/src/pages/api/transactions/[id]/index.ts
@@ -32,67 +32,76 @@ export const GET: APIRoute = async ({ params }) => {
   }
 };
 
-export const PUT: APIRoute = async ({ request, params }) => {
-  const { id } = params;
-
+const validateRequestParams = (id: string | undefined) => {
   if (!id) {
     return new Response(JSON.stringify({ error: 'Transaction ID is required' }), {
       status: 400,
       headers: { 'Content-Type': 'application/json' },
     });
   }
+  return null;
+};
+
+const validateTransaction = async (
+  id: string,
+  transactionService: typeof import('@data/db.service').transactionService,
+) => {
+  const existingTransaction = await transactionService.getById(id);
+  if (!existingTransaction) {
+    return new Response(JSON.stringify({ error: 'Transaction not found' }), {
+      status: 404,
+      headers: { 'Content-Type': 'application/json' },
+    });
+  }
+  return existingTransaction;
+};
+
+const prepareUpdateData = (updates: Partial<Transaction>) => {
+  const updatedData: Partial<{
+    accountId: string;
+    date: Date;
+    description: string;
+    amount: number;
+    category: string | undefined;
+    status: TransactionStatus | undefined;
+    type: TransactionType | undefined;
+    notes: string | undefined;
+    tags: string | undefined;
+  }> = {};
+
+  if (updates.accountId !== undefined) updatedData.accountId = updates.accountId;
+  if (updates.description !== undefined) updatedData.description = updates.description;
+  if (updates.amount !== undefined) updatedData.amount = Number(updates.amount);
+  if (updates.category !== undefined) updatedData.category = updates.category || undefined;
+  if (updates.notes !== undefined) updatedData.notes = updates.notes || undefined;
+  if (updates.tags !== undefined) updatedData.tags = updates.tags || undefined;
+
+  if (updates.date !== undefined) {
+    updatedData.date = typeof updates.date === 'string' ? new Date(updates.date) : updates.date;
+  }
+
+  if (updates.status !== undefined) {
+    updatedData.status = updates.status as TransactionStatus;
+  }
+
+  if (updates.type !== undefined) {
+    updatedData.type = updates.type as TransactionType;
+  }
+
+  return updatedData;
+};
+
+export const PUT: APIRoute = async ({ request, params }) => {
+  const validationError = validateRequestParams(params.id);
+  if (validationError) return validationError;
 
   try {
     const updates = (await request.json()) as Partial<Transaction>;
+    const existingTransaction = await validateTransaction(params.id as string, transactionService);
+    if (existingTransaction instanceof Response) return existingTransaction;
 
-    // Check if transaction exists
-    const existingTransaction = await transactionService.getById(id);
-
-    if (!existingTransaction) {
-      return new Response(JSON.stringify({ error: 'Transaction not found' }), {
-        status: 404,
-        headers: { 'Content-Type': 'application/json' },
-      });
-    }
-
-    // Create a properly typed update object
-    const updatedData: Partial<{
-      accountId: string;
-      date: Date;
-      description: string;
-      amount: number;
-      category: string | undefined;
-      status: TransactionStatus | undefined;
-      type: TransactionType | undefined;
-      notes: string | undefined;
-      tags: string | undefined;
-    }> = {};
-
-    // Copy the properties we want to update
-    if (updates.accountId !== undefined) updatedData.accountId = updates.accountId;
-    if (updates.description !== undefined) updatedData.description = updates.description;
-    if (updates.amount !== undefined) updatedData.amount = Number(updates.amount);
-    if (updates.category !== undefined) updatedData.category = updates.category || undefined;
-    if (updates.notes !== undefined) updatedData.notes = updates.notes || undefined;
-    if (updates.tags !== undefined) updatedData.tags = updates.tags || undefined;
-
-    // Convert date to Date object if it's a string
-    if (updates.date !== undefined) {
-      updatedData.date = typeof updates.date === 'string' ? new Date(updates.date) : updates.date;
-    }
-
-    // Cast status and type to enum types if provided
-    if (updates.status !== undefined) {
-      updatedData.status = updates.status as TransactionStatus;
-    }
-
-    if (updates.type !== undefined) {
-      updatedData.type = updates.type as TransactionType;
-    }
-
-    // Update the transaction using the service
-    // The service will automatically handle account balance adjustments
-    const updatedTransaction = await transactionService.update(id, updatedData);
+    const updatedData = prepareUpdateData(updates);
+    const updatedTransaction = await transactionService.update(params.id as string, updatedData);
 
     if (!updatedTransaction) {
       return new Response(JSON.stringify({ error: 'Failed to update transaction' }), {
@@ -101,7 +110,6 @@ export const PUT: APIRoute = async ({ request, params }) => {
       });
     }
 
-    // Convert Decimal to number for response
     const response = {
       ...updatedTransaction,
       amount: Number(updatedTransaction.amount),
diff --git a/src/pages/index.astro b/src/pages/index.astro
index 1163ee6..cb4bddb 100644
--- a/src/pages/index.astro
+++ b/src/pages/index.astro
@@ -1,8 +1,5 @@
 ---
-import MainContent from "../components/MainContent.astro";
-import Sidebar from "../components/Sidebar.astro";
-import BaseLayout from "../layouts/BaseLayout.astro";
-import type { Account, Transaction } from "../types";
+import type { Account, Transaction } from '@types';
 
 // Get the base URL from the incoming request
 const baseUrl = new URL(Astro.request.url).origin;
@@ -13,20 +10,20 @@ const accounts: Account[] = await accountsResponse.json();
 
 // Initialize with first account or empty account if none exist
 const initialAccount: Account = accounts[0] || {
-    id: "",
-    name: "No accounts available",
-    accountNumber: "000000",
-    balance: 0,
-    bankName: "",
+  id: '',
+  name: 'No accounts available',
+  accountNumber: '000000',
+  balance: 0,
+  bankName: '',
 };
 
 // Fetch initial transactions if we have an account, using absolute URL
 let initialTransactions: Transaction[] = [];
 if (initialAccount.id) {
-    const transactionsResponse = await fetch(
-        `${baseUrl}/api/accounts/${initialAccount.id}/transactions`,
-    );
-    initialTransactions = await transactionsResponse.json();
+  const transactionsResponse = await fetch(
+    `${baseUrl}/api/accounts/${initialAccount.id}/transactions`,
+  );
+  initialTransactions = await transactionsResponse.json();
 }
 ---
 
@@ -44,7 +41,7 @@ if (initialAccount.id) {
         setTransactions,
         loadTransactionsForAccount,
         startEditingTransaction,
-    } from "../stores/transactionStore";
+    } from "@stores/transactionStore";
 
     // Access server-rendered data which is available as globals
     const initialAccountData = JSON.parse(
diff --git a/src/server.ts b/src/server.ts
index 52310d9..a064b59 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -1,6 +1,3 @@
-// src/server.ts
-
-import { IncomingMessage, Server, ServerResponse } from 'http';
 import { type BankAccount, PrismaClient } from '@prisma/client';
 import dotenv from 'dotenv';
 import Fastify, { type FastifyInstance } from 'fastify';
@@ -56,9 +53,16 @@ server.post(
       });
       reply.code(201);
       return newAccount;
-    } catch (error: any) {
+    } catch (error: unknown) {
       server.log.error(error);
-      if (error.code === 'P2002' && error.meta?.target?.includes('accountNumber')) {
+      if (
+        typeof error === 'object' &&
+        error !== null &&
+        'code' in error &&
+        error.code === 'P2002' &&
+        'meta' in error &&
+        error.meta?.target?.includes('accountNumber')
+      ) {
         reply.code(409);
         const body = createBankAccountSchema.parse(request.body);
         throw new Error(`Bank account with number ${body.accountNumber} already exists.`);
@@ -97,14 +101,26 @@ server.post(
         data: updateData,
       });
       return updatedAccount;
-    } catch (error: any) {
+    } catch (error: unknown) {
       server.log.error(error);
-      if (error.code === 'P2025') {
+      if (
+        typeof error === 'object' &&
+        error !== null &&
+        'code' in error &&
+        error.code === 'P2025'
+      ) {
         // Record to update not found
         reply.code(404);
         throw new Error(`Bank account with ID ${request.params.id} not found.`);
       }
-      if (error.code === 'P2002' && error.meta?.target?.includes('accountNumber')) {
+      if (
+        typeof error === 'object' &&
+        error !== null &&
+        'code' in error &&
+        error.code === 'P2002' &&
+        'meta' in error &&
+        error.meta?.target?.includes('accountNumber')
+      ) {
         reply.code(409);
         // Access accountNumber safely as it's optional in update
         const attemptedNumber = request.body.accountNumber || '(unchanged)';
@@ -139,9 +155,14 @@ server.delete(
         where: { id: id }, // Use the validated numeric ID
       });
       return { message: `Bank account with ID ${id} deleted successfully.`, deletedAccount };
-    } catch (error: any) {
+    } catch (error: unknown) {
       server.log.error(error);
-      if (error.code === 'P2025') {
+      if (
+        typeof error === 'object' &&
+        error !== null &&
+        'code' in error &&
+        error.code === 'P2025'
+      ) {
         // Record to delete not found
         reply.code(404);
         throw new Error(`Bank account with ID ${request.params.id} not found.`);
@@ -165,7 +186,7 @@ server.get(`${API_PREFIX}/`, async (request, reply): Promise<BankAccount[]> => {
       orderBy: { createdAt: 'desc' },
     });
     return accounts;
-  } catch (error: any) {
+  } catch (error: unknown) {
     server.log.error(error);
     reply.code(500);
     throw new Error('Failed to retrieve bank accounts.');
@@ -195,7 +216,7 @@ server.get(
         throw new Error(`Bank account with ID ${id} not found.`);
       }
       return account;
-    } catch (error: any) {
+    } catch (error: unknown) {
       // Handle Zod validation errors (though should be caught by Fastify earlier)
       if (error instanceof z.ZodError) {
         reply.code(400);
diff --git a/src/stores/transactionStore.ts b/src/stores/transactionStore.ts
index 384f5a4..a1ba7be 100644
--- a/src/stores/transactionStore.ts
+++ b/src/stores/transactionStore.ts
@@ -1,5 +1,5 @@
+import type { Transaction } from '@types';
 import { atom } from 'nanostores';
-import type { Transaction } from '../types';
 
 // Atom to hold the ID of the currently selected account
 export const currentAccountId = atom<string | null>(null);
diff --git a/src/styles/global.css b/src/styles/global.css
index 43de209..7ab20c8 100644
--- a/src/styles/global.css
+++ b/src/styles/global.css
@@ -1,67 +1,156 @@
-/* Paste the CSS from style-alt3.css here */
+/* Mobile-first styles */
 body {
   font-family: system-ui, sans-serif;
   line-height: 1.6;
   margin: 0;
   background-color: #f0f2f5;
   color: #333;
+  height: 100%;
+  overflow: hidden;
 }
 
+html {
+  height: 100%;
+  box-sizing: border-box;
+}
+
+*,
+*:before,
+*:after {
+  box-sizing: inherit;
+}
+
+/* Mobile-first: Dashboard starts as column layout */
 .dashboard-layout {
   display: flex;
-  min-height: 100vh;
+  flex-direction: column;
+  height: 100vh;
+  overflow: hidden;
+  width: 100%;
 }
 
+/* Mobile-first sidebar */
 .sidebar {
-  width: 280px;
+  width: 100%;
   background-color: #ffffff;
-  border-right: 1px solid #e0e0e0;
+  border-bottom: 1px solid #e0e0e0;
   display: flex;
   flex-direction: column;
-  padding: 20px;
-  box-shadow: 2px 0 5px rgba(0, 0, 0, 0.05);
-  /* Ensure sidebar doesn't shrink */
-  flex-shrink: 0;
+  padding: 15px;
+  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
+  /* Allow scrolling on mobile */
+  overflow-y: auto;
+  max-height: 60vh; /* Limit height on mobile */
+  transition: max-height 0.3s ease;
+  z-index: 10;
 }
 
-.sidebar-header h2 {
-  margin: 0 0 20px 0;
-  color: #0056b3;
+.sidebar-collapsed {
+  max-height: 180px; /* Just enough for header and account selector */
 }
+
+.sidebar-toggle {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 100%;
+  background-color: #f3f4f6;
+  border: none;
+  border-top: 1px solid #e0e0e0;
+  border-bottom: 1px solid #e0e0e0;
+  color: #555;
+  padding: 8px;
+  font-size: 0.9em;
+  cursor: pointer;
+  position: relative;
+  z-index: 20;
+  text-align: center;
+}
+
+.sidebar-toggle span {
+  pointer-events: none; /* Ensure clicks register on the button, not inner elements */
+}
+
+.sidebar-toggle-icon {
+  display: inline-block;
+  margin-left: 5px;
+  transition: transform 0.3s ease;
+  pointer-events: none; /* Ensure icon doesn't interfere with clicks */
+}
+
+.sidebar-toggle[aria-expanded="false"] .sidebar-toggle-icon {
+  transform: rotate(180deg);
+}
+
+/* Sidebar header */
+.sidebar-header h2 {
+  margin: 0 0 15px 0;
+  color: #0056b3;
+  font-size: 1.5em;
+}
+
 .account-nav h3 {
   margin-top: 0;
   margin-bottom: 10px;
   font-size: 1em;
   color: #555;
 }
+
 .account-nav select {
   width: 100%;
   padding: 10px;
   border: 1px solid #ccc;
   border-radius: 4px;
-  margin-bottom: 25px;
+  margin-bottom: 15px;
   font-size: 1em;
 }
 
 .add-transaction-section {
-  margin-bottom: 25px;
+  margin-bottom: 15px;
   border: 1px solid #e0e0e0;
   border-radius: 5px;
+  transition: max-height 0.3s ease;
 }
+
+/* Collapsible sections */
+.collapsible-section {
+  max-height: 1000px; /* Large enough to contain content */
+  overflow: hidden;
+  transition: max-height 0.3s ease-out;
+}
+
+.collapsed {
+  max-height: 0;
+}
+
+/* Toggle button for add transaction form */
 .toggle-form-btn {
   background-color: #f8f9fa;
   color: #0056b3;
   border: none;
   border-bottom: 1px solid #e0e0e0;
-  padding: 12px 15px;
+  padding: 10px;
   width: 100%;
   text-align: left;
   font-size: 1em;
   cursor: pointer;
   border-radius: 5px 5px 0 0;
   font-weight: 500;
-  display: block; /* Ensure it takes full width */
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
 }
+
+.toggle-form-btn::after {
+  content: "▼";
+  font-size: 0.8em;
+  transition: transform 0.3s ease;
+}
+
+.toggle-form-btn[aria-expanded="false"]::after {
+  transform: rotate(180deg);
+}
+
 .toggle-form-btn:hover {
   background-color: #e9ecef;
 }
@@ -69,44 +158,48 @@ body {
 .collapsible-form {
   padding: 15px;
   background-color: #fdfdfd;
-  transition: max-height 0.3s ease-out, opacity 0.3s ease-out, padding 0.3s ease-out, border 0.3s
-    ease-out;
+  transition: max-height 0.3s ease-out, opacity 0.3s ease-out, padding 0.3s ease-out;
   overflow: hidden;
   max-height: 500px;
   opacity: 1;
-  border-top: 1px solid #e0e0e0; /* Start with border */
+  border-top: 1px solid #e0e0e0;
 }
+
 .collapsible-form.collapsed {
   max-height: 0;
   opacity: 0;
   padding-top: 0;
   padding-bottom: 0;
-  border-top-color: transparent; /* Hide border when collapsed */
 }
+
 .collapsible-form h4 {
   margin-top: 0;
   margin-bottom: 15px;
   font-size: 1.1em;
 }
+
 .form-group {
   margin-bottom: 12px;
 }
+
 .form-group label {
   display: block;
   margin-bottom: 4px;
   font-size: 0.9em;
   color: #555;
 }
+
 .form-group input[type="date"],
 .form-group input[type="text"],
 .form-group input[type="number"] {
-  width: calc(100% - 18px); /* Account for padding */
+  width: 100%;
   padding: 8px;
   border: 1px solid #ccc;
   border-radius: 3px;
   font-size: 0.95em;
-  box-sizing: border-box; /* Include padding in width calculation */
+  box-sizing: border-box;
 }
+
 .collapsible-form button[type="submit"] {
   background-color: #007bff;
   color: white;
@@ -116,109 +209,241 @@ body {
   cursor: pointer;
   margin-top: 5px;
 }
+
 .collapsible-form button[type="submit"]:hover {
   background-color: #0056b3;
 }
 
 .account-summary {
-  padding-top: 20px;
+  padding-top: 10px;
   border-top: 1px solid #eee;
+  margin-bottom: 15px;
 }
-.account-summary h4 {
-  margin: 0 0 10px 0;
+
+.account-summary-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 5px;
+}
+
+.account-summary-header h4 {
+  margin: 0;
   font-size: 1em;
   color: #555;
+  flex: 1;
 }
+
+#account-balance {
+  font-weight: bold;
+  color: #333;
+  font-size: 1.1em;
+}
+
 .account-summary p {
   margin: 5px 0;
   font-size: 0.95em;
 }
-#account-balance {
-  font-weight: bold;
-  color: #333;
-}
 
 .main-content {
   flex-grow: 1;
-  padding: 20px 30px;
+  padding: 15px;
   overflow-y: auto;
+  width: 100%;
 }
+
 .main-header {
-  margin-bottom: 20px;
-  padding-bottom: 15px;
+  margin-bottom: 15px;
+  padding-bottom: 10px;
   border-bottom: 1px solid #eee;
 }
+
 .main-header h1 {
   margin: 0;
-  font-size: 1.8em;
+  font-size: 1.5em;
   font-weight: 500;
   color: #333;
 }
+
 #current-account-name {
   font-style: italic;
-} /* Example styling */
+}
 
 .transaction-list {
   background-color: #fff;
-  padding: 20px;
+  padding: 10px;
   border-radius: 5px;
   box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
+  overflow-x: auto; /* Enable horizontal scrolling for table on mobile */
 }
+
 table {
   width: 100%;
   border-collapse: collapse;
+  min-width: 500px; /* Ensure minimum width for better mobile experience */
 }
+
 th,
 td {
-  padding: 12px 15px;
+  padding: 8px 10px;
   text-align: left;
   border-bottom: 1px solid #eee;
+  font-size: 0.9rem; /* Slightly smaller text on mobile */
 }
+
 th {
   background-color: #f8f9fa;
   font-weight: 600;
-  font-size: 0.9em;
+  font-size: 0.85em;
   text-transform: uppercase;
   color: #555;
+  white-space: nowrap;
 }
+
 tbody tr:hover {
   background-color: #f1f3f5;
 }
+
 .amount-col {
   text-align: right;
 }
+
 .amount-positive {
   color: #198754;
   font-weight: 500;
 }
+
 .amount-negative {
   color: #dc3545;
   font-weight: 500;
 }
+
+/* Mobile Transaction Cards */
+.transaction-cards {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.transaction-card {
+  background-color: #fff;
+  border-radius: 8px;
+  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12);
+  padding: 12px;
+  position: relative;
+}
+
+.transaction-card-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 8px;
+}
+
+.transaction-card-date {
+  font-size: 0.85rem;
+  color: #555;
+  font-weight: 500;
+}
+
+.transaction-card-amount {
+  font-weight: 600;
+  font-size: 1.1rem;
+}
+
+.transaction-card-description {
+  font-size: 1rem;
+  font-weight: 500;
+  margin-bottom: 4px;
+  word-break: break-word;
+}
+
+.transaction-card-category {
+  font-size: 0.85rem;
+  color: #666;
+  margin-bottom: 0; /* Reduce space below category */
+  display: inline-block; /* Allow actions to float beside it */
+}
+
+.transaction-card-label {
+  color: #777;
+  font-size: 0.8rem;
+}
+
+.transaction-card-actions {
+  display: flex;
+  justify-content: flex-end;
+  gap: 8px;
+  margin-top: 0; /* Remove top margin */
+  float: right; /* Float actions to the right of category */
+}
+
+.empty-message,
+.loading-message {
+  text-align: center;
+  padding: 20px;
+  color: #666;
+  background-color: #fff;
+  border-radius: 8px;
+  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
+}
+
+/* Mobile-optimized action buttons */
 .action-btn {
-  padding: 4px 8px;
-  margin-right: 5px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  padding: 6px;
+  margin-right: 3px;
   cursor: pointer;
-  border-radius: 3px;
+  border-radius: 4px;
   border: 1px solid #ccc;
   font-size: 0.85em;
+  min-height: 32px;
+  min-width: 32px;
 }
+
+.button-text {
+  display: none; /* Hide text on mobile by default */
+}
+
+.action-btn:hover {
+  transform: translateY(-1px);
+}
+
+.action-btn:active {
+  transform: translateY(0);
+}
+
+.button-icon {
+  flex-shrink: 0;
+}
+
 .edit-btn {
   background-color: #e9ecef;
   color: #333;
 }
+
+.edit-btn:hover {
+  background-color: #dde1e4;
+}
+
 .delete-btn {
   background-color: #f8d7da;
   color: #721c24;
   border-color: #f5c6cb;
 }
 
+.delete-btn:hover {
+  background-color: #f5c2c7;
+}
+
 .error-message {
   color: #dc3545;
   background-color: #f8d7da;
   border: 1px solid #f5c6cb;
   border-radius: 4px;
-  padding: 8px 12px;
+  padding: 8px;
   margin-bottom: 15px;
   font-size: 0.9em;
 }
@@ -228,7 +453,7 @@ tbody tr:hover {
   background-color: #d1e7dd;
   border: 1px solid #badbcc;
   border-radius: 4px;
-  padding: 8px 12px;
+  padding: 8px;
   margin-bottom: 15px;
   font-size: 0.9em;
 }
@@ -265,23 +490,42 @@ tbody tr:hover {
   font-size: 0.85em;
 }
 
-/* Basic Responsive */
-@media (max-width: 768px) {
-  .dashboard-layout {
-    flex-direction: column;
-  }
-  .sidebar {
-    width: 100%;
-    border-right: none;
-    border-bottom: 1px solid #e0e0e0;
-    max-height: none; /* Allow sidebar to grow */
-  }
-  .account-summary {
-    margin-top: 20px;
-  } /* Adjust spacing */
-  .main-content {
-    padding: 20px;
-  }
+/* Toast notifications - positioned better for mobile */
+.toast-viewport {
+  position: fixed;
+  bottom: 10px;
+  right: 10px;
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+  width: calc(100% - 20px);
+  max-width: 350px;
+  margin: 0;
+  list-style: none;
+  z-index: 2147483647;
+  outline: none;
+}
+
+.toast-root {
+  background-color: white;
+  border-radius: 6px;
+  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
+  padding: 15px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+}
+
+.toast-title {
+  margin: 0;
+  font-weight: 500;
+}
+
+.toast-close-button {
+  border: none;
+  background: transparent;
+  cursor: pointer;
+  color: #999;
 }
 
 /* Loading States */
@@ -328,3 +572,69 @@ tbody tr:hover {
   right: 10px;
   border-width: 2px;
 }
+
+/* Tablet breakpoint */
+@media (min-width: 640px) {
+  .sidebar {
+    padding: 20px;
+    max-height: none;
+  }
+
+  .main-content {
+    padding: 20px;
+  }
+
+  th,
+  td {
+    padding: 10px 12px;
+    font-size: 1rem;
+  }
+
+  .action-btn {
+    padding: 6px 8px;
+    margin-right: 5px;
+  }
+
+  .button-text {
+    display: none; /* Still hide text on tablets */
+  }
+}
+
+/* Desktop breakpoint */
+@media (min-width: 1024px) {
+  .dashboard-layout {
+    flex-direction: row;
+  }
+
+  .sidebar {
+    width: 300px;
+    border-right: 1px solid #e0e0e0;
+    border-bottom: none;
+    max-height: 100vh;
+  }
+
+  .sidebar-toggle {
+    display: none; /* Hide sidebar toggle on desktop */
+  }
+
+  .collapsible-section {
+    max-height: none !important; /* Always expanded on desktop */
+  }
+
+  .main-content {
+    padding: 25px 30px;
+  }
+
+  .action-btn {
+    padding: 6px 12px;
+  }
+
+  .button-text {
+    display: inline; /* Show text on desktop */
+    margin-left: 5px;
+  }
+
+  .sidebar-header h2 {
+    font-size: 1.8em;
+  }
+}
diff --git a/src/styles/radix-ui.css b/src/styles/radix-ui.css
new file mode 100644
index 0000000..4c82a94
--- /dev/null
+++ b/src/styles/radix-ui.css
@@ -0,0 +1,189 @@
+/* Radix UI Form Styles */
+.form-root {
+  width: 100%;
+  box-sizing: border-box;
+}
+
+.form-field {
+  display: flex;
+  flex-direction: column;
+  margin-bottom: 16px;
+  width: 100%;
+}
+
+.form-label {
+  font-size: 14px;
+  font-weight: 500;
+  margin-bottom: 6px;
+  color: #333;
+}
+
+.form-message {
+  font-size: 12px;
+  color: #e11d48;
+}
+
+.form-input {
+  padding: 8px 12px;
+  border-radius: 4px;
+  border: 1px solid #d1d5db;
+  font-size: 14px;
+  width: 100%;
+  box-sizing: border-box;
+  background-color: white;
+  transition: border-color 0.2s;
+  height: 38px; /* Match height of dropdown */
+}
+
+.form-input:focus {
+  outline: none;
+  border-color: #2563eb;
+  box-shadow: 0 0 0 1px rgba(37, 99, 235, 0.2);
+}
+
+.form-input:disabled {
+  background-color: #f3f4f6;
+  cursor: not-allowed;
+}
+
+/* Amount input specific styling */
+.amount-input-wrapper {
+  position: relative;
+  display: flex;
+  align-items: center;
+  width: 100%;
+}
+
+.currency-symbol {
+  position: absolute;
+  left: 12px;
+  color: #666;
+  font-size: 14px;
+}
+
+.amount-input {
+  padding-left: 24px;
+}
+
+/* Toast Notifications */
+.toast-viewport {
+  position: fixed;
+  bottom: 0;
+  right: 0;
+  display: flex;
+  flex-direction: column;
+  padding: 16px;
+  gap: 8px;
+  width: 390px;
+  max-width: 100vw;
+  margin: 0;
+  list-style: none;
+  z-index: 2147483647;
+  outline: none;
+}
+
+.toast-root {
+  background-color: #fff;
+  border-radius: 6px;
+  box-shadow: 0px 4px 12px rgba(0, 0, 0, 0.1);
+  padding: 12px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  border-left: 4px solid #22c55e;
+  margin-bottom: 8px;
+}
+
+.toast-title {
+  font-weight: 500;
+  color: #111;
+  font-size: 14px;
+}
+
+.toast-close-button {
+  background: transparent;
+  border: none;
+  color: #666;
+  cursor: pointer;
+  padding: 4px;
+  border-radius: 4px;
+}
+
+.toast-close-button:hover {
+  background-color: #f3f4f6;
+}
+
+/* Error message */
+.error-message {
+  background-color: #fee2e2;
+  color: #b91c1c;
+  padding: 8px 12px;
+  border-radius: 4px;
+  margin-bottom: 16px;
+  font-size: 14px;
+  border-left: 4px solid #b91c1c;
+  width: 100%;
+  box-sizing: border-box;
+}
+
+/* Form Actions */
+.form-actions {
+  display: flex;
+  justify-content: space-between;
+  gap: 8px;
+  margin-top: 16px;
+  width: 100%;
+}
+
+.cancel-btn {
+  padding: 8px 16px;
+  background-color: transparent;
+  border: 1px solid #d1d5db;
+  border-radius: 4px;
+  font-size: 14px;
+  color: #4b5563;
+  cursor: pointer;
+  transition: background-color 0.2s;
+  height: 38px;
+  flex: 1;
+}
+
+.cancel-btn:hover:not(:disabled) {
+  background-color: #f3f4f6;
+}
+
+.submit-btn {
+  padding: 8px 16px;
+  background-color: #2563eb;
+  border: none;
+  border-radius: 4px;
+  font-size: 14px;
+  color: white;
+  cursor: pointer;
+  transition: background-color 0.2s;
+  height: 38px;
+  flex: 1;
+}
+
+.submit-btn:hover:not(:disabled) {
+  background-color: #1d4ed8;
+}
+
+.submit-btn:disabled,
+.cancel-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+/* Sidebar component adjustments */
+.sidebar select,
+.sidebar button,
+.sidebar input {
+  width: 100%;
+  box-sizing: border-box;
+}
+
+/* Make date picker fill entire width */
+input[type="date"].form-input {
+  width: 100%;
+}
diff --git a/src/test/components.test.tsx b/src/test/components.test.tsx
index 2c74b51..d9209cf 100644
--- a/src/test/components.test.tsx
+++ b/src/test/components.test.tsx
@@ -1,8 +1,8 @@
+import AddTransactionForm from '@components/AddTransactionForm';
+import TransactionTable from '@components/TransactionTable';
 import { act, cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react';
+import type { Transaction } from '@types';
 import { describe, expect, it, vi } from 'vitest';
-import AddTransactionForm from '../components/AddTransactionForm';
-import TransactionTable from '../components/TransactionTable';
-import type { Transaction } from '../types';
 
 // Create hoisted mocks that are safe to use in vi.mock
 const createMocks = vi.hoisted(() => ({
@@ -34,7 +34,7 @@ vi.mock('@nanostores/react', () => ({
   useStore: createMocks.useStore,
 }));
 
-vi.mock('../stores/transactionStore', () => ({
+vi.mock('@stores/transactionStore', () => ({
   currentAccountId: createMocks.currentAccountId,
   transactionToEdit: createMocks.transactionToEdit,
   refreshKey: createMocks.refreshKey,
diff --git a/src/types/events.ts b/src/types/events.ts
index 3e73163..1eee85b 100644
--- a/src/types/events.ts
+++ b/src/types/events.ts
@@ -1,4 +1,4 @@
-import type { Transaction } from '../types';
+import type { Transaction } from '@types';
 
 export interface TransactionEventDetail {
   transaction: Transaction;