diff --git a/main.js b/main.js
index ea1539c..f1d260e 100644
--- a/main.js
+++ b/main.js
@@ -12,6 +12,12 @@ let loginWindow = null;
 let silentLoginWindow = null;
 let settingsWindow = null;
 let tray = null;
+let iconGeneratorWindow = null;
+
+// Tray icon state
+let cachedUsageData = null;
+let trayUpdateInterval = null;
+let lastTrayUpdate = 0;
 
 // Window configuration
 const WIDGET_WIDTH = 480;
@@ -323,6 +329,117 @@ async function attemptSilentLogin() {
   });
 }
 
+// Create hidden window for generating tray icons
+function createIconGeneratorWindow() {
+  if (iconGeneratorWindow) return;
+
+  iconGeneratorWindow = new BrowserWindow({
+    width: 100,
+    height: 100,
+    show: false,
+    webPreferences: {
+      nodeIntegration: true,
+      contextIsolation: false
+    }
+  });
+
+  iconGeneratorWindow.loadFile(path.join(__dirname, 'src/icon-generator.html'));
+
+  iconGeneratorWindow.on('closed', () => {
+    iconGeneratorWindow = null;
+  });
+}
+
+// Generate tray icon with circular progress indicator
+async function generateTrayIcon(percentage, colors, showText = true) {
+  const { nativeImage } = require('electron');
+
+  if (!iconGeneratorWindow) {
+    createIconGeneratorWindow();
+    // Wait for window to load
+    await new Promise(resolve => setTimeout(resolve, 1000));
+  }
+
+  return new Promise((resolve) => {
+    ipcMain.once('icon-generated', (event, dataUrl) => {
+      resolve(nativeImage.createFromDataURL(dataUrl));
+    });
+
+    iconGeneratorWindow.webContents.send('generate-icon', { percentage, colors, showText });
+  });
+}
+
+// Update tray icon with current usage data
+async function updateTrayIcon() {
+  if (!tray) return;
+
+  // If no data yet, show default icon
+  if (!cachedUsageData) {
+    tray.setImage(path.join(__dirname, 'assets/tray-icon.png'));
+    tray.setToolTip('Claude Usage Widget - Loading...');
+    return;
+  }
+
+  // Get tray settings from store
+  const traySettings = store.get('traySettings', {
+    displayMode: 'session',
+    showText: false,
+    colors: {
+      normal: { start: '#8b5cf6', end: '#a78bfa' },
+      warning: { start: '#f59e0b', end: '#fbbf24' },
+      danger: { start: '#ef4444', end: '#f87171' }
+    }
+  });
+
+  // Get appropriate usage data based on display mode
+  let percentage, resetsAt;
+  if (traySettings.displayMode === 'weekly') {
+    percentage = cachedUsageData.seven_day?.utilization || 0;
+    resetsAt = cachedUsageData.seven_day?.resets_at;
+  } else {
+    percentage = cachedUsageData.five_hour?.utilization || 0;
+    resetsAt = cachedUsageData.five_hour?.resets_at;
+  }
+
+  // Generate and set new icon
+  try {
+    const icon = await generateTrayIcon(percentage, traySettings.colors, traySettings.showText);
+    tray.setImage(icon);
+
+    // Update tooltip with detailed info
+    const modeLabel = traySettings.displayMode === 'weekly' ? '7-day' : '5-hour';
+    const resetTime = resetsAt ? new Date(resetsAt).toLocaleString() : 'N/A';
+    tray.setToolTip(
+      `Claude Usage: ${Math.round(percentage)}% (${modeLabel})\nResets: ${resetTime}`
+    );
+  } catch (error) {
+    console.error('Failed to generate tray icon:', error);
+  }
+}
+
+// Throttled tray update to avoid excessive updates
+function updateTrayIconThrottled() {
+  const now = Date.now();
+  const interval = store.get('trayUpdateInterval', 30) * 1000; // Convert to ms
+
+  if (now - lastTrayUpdate >= interval) {
+    updateTrayIcon();
+    lastTrayUpdate = now;
+  }
+}
+
+// Start periodic tray icon updates
+function startTrayUpdateTimer() {
+  if (trayUpdateInterval) clearInterval(trayUpdateInterval);
+
+  const interval = store.get('trayUpdateInterval', 30) * 1000;
+  trayUpdateInterval = setInterval(() => {
+    if (cachedUsageData) {
+      updateTrayIcon();
+    }
+  }, interval);
+}
+
 function createTray() {
   try {
     tray = new Tray(path.join(__dirname, 'assets/tray-icon.png'));
@@ -559,10 +676,71 @@ ipcMain.handle('fetch-usage-data', async () => {
   }
 });
 
+// Tray icon IPC handlers
+ipcMain.on('usage-data-update', (event, data) => {
+  cachedUsageData = data;
+  updateTrayIconThrottled();
+});
+
+ipcMain.handle('get-tray-settings', () => {
+  return store.get('traySettings', {
+    displayMode: 'session',
+    showText: false,
+    colors: {
+      normal: { start: '#8b5cf6', end: '#a78bfa' },
+      warning: { start: '#f59e0b', end: '#fbbf24' },
+      danger: { start: '#ef4444', end: '#f87171' }
+    }
+  });
+});
+
+ipcMain.on('set-tray-settings', (event, settings) => {
+  store.set('traySettings', settings);
+  updateTrayIcon(); // Immediate update
+});
+
+ipcMain.handle('get-tray-update-interval', () => {
+  return store.get('trayUpdateInterval', 30);
+});
+
+ipcMain.on('set-tray-update-interval', (event, seconds) => {
+  store.set('trayUpdateInterval', seconds);
+  startTrayUpdateTimer(); // Restart timer with new interval
+});
+
+// Theme settings IPC handlers
+ipcMain.handle('get-theme-settings', () => {
+  return store.get('themeSettings', {
+    backgroundStart: '#1e1e2e',
+    backgroundEnd: '#2a2a3e',
+    textPrimary: '#e0e0e0',
+    textSecondary: '#a0a0a0',
+    titleBarBg: '#000000',
+    titleBarOpacity: 30,
+    borderColor: '#ffffff',
+    borderOpacity: 10
+  });
+});
+
+ipcMain.handle('set-theme-settings', (event, theme) => {
+  store.set('themeSettings', theme);
+  return true;
+});
+
+ipcMain.handle('notify-theme-change', (event, theme) => {
+  // Notify main window to update theme
+  if (mainWindow && !mainWindow.isDestroyed()) {
+    mainWindow.webContents.send('theme-changed', theme);
+  }
+  return true;
+});
+
 // App lifecycle
 app.whenReady().then(() => {
   createMainWindow();
   createTray();
+  createIconGeneratorWindow();
+  startTrayUpdateTimer();
 
   // Check if we have credentials
   // const hasCredentials = store.get('sessionKey') && store.get('organizationId');
@@ -573,6 +751,15 @@ app.whenReady().then(() => {
   // }
 });
 
+app.on('before-quit', () => {
+  if (trayUpdateInterval) {
+    clearInterval(trayUpdateInterval);
+  }
+  if (iconGeneratorWindow && !iconGeneratorWindow.isDestroyed()) {
+    iconGeneratorWindow.destroy();
+  }
+});
+
 app.on('window-all-closed', () => {
   // Don't quit on macOS
   if (process.platform !== 'darwin') {
diff --git a/preload.js b/preload.js
index be50ebf..5993823 100644
--- a/preload.js
+++ b/preload.js
@@ -45,5 +45,20 @@ contextBridge.exposeInMainWorld('electronAPI', {
   notifyColorChange: (preferences) => ipcRenderer.invoke('notify-color-change', preferences),
   onColorsChanged: (callback) => {
     ipcRenderer.on('colors-changed', (event, preferences) => callback(preferences));
+  },
+
+  // Tray icon
+  sendUsageToMain: (data) => ipcRenderer.send('usage-data-update', data),
+  getTraySettings: () => ipcRenderer.invoke('get-tray-settings'),
+  setTraySettings: (settings) => ipcRenderer.send('set-tray-settings', settings),
+  getTrayUpdateInterval: () => ipcRenderer.invoke('get-tray-update-interval'),
+  setTrayUpdateInterval: (seconds) => ipcRenderer.send('set-tray-update-interval', seconds),
+
+  // Theme settings
+  getThemeSettings: () => ipcRenderer.invoke('get-theme-settings'),
+  setThemeSettings: (theme) => ipcRenderer.invoke('set-theme-settings', theme),
+  notifyThemeChange: (theme) => ipcRenderer.invoke('notify-theme-change', theme),
+  onThemeChanged: (callback) => {
+    ipcRenderer.on('theme-changed', (event, theme) => callback(theme));
   }
 });
diff --git a/src/icon-generator.html b/src/icon-generator.html
new file mode 100644
index 0000000..5e69aa8
--- /dev/null
+++ b/src/icon-generator.html
@@ -0,0 +1,86 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="UTF-8">
+  <title>Icon Generator</title>
+</head>
+<body>
+  <canvas id="iconCanvas" width="128" height="128"></canvas>
+  <script>
+    const { ipcRenderer } = require('electron');
+    const canvas = document.getElementById('iconCanvas');
+    const ctx = canvas.getContext('2d');
+
+    ipcRenderer.on('generate-icon', (event, { percentage, colors, showText }) => {
+      // Clear canvas
+      ctx.clearRect(0, 0, 128, 128);
+
+      const centerX = 64;
+      const centerY = 64;
+      const radius = 58;
+
+      // Determine colors based on percentage
+      let startColor, endColor;
+      if (percentage >= 90) {
+        startColor = colors.danger.start;
+        endColor = colors.danger.end;
+      } else if (percentage >= 75) {
+        startColor = colors.warning.start;
+        endColor = colors.warning.end;
+      } else {
+        startColor = colors.normal.start;
+        endColor = colors.normal.end;
+      }
+
+      // Draw background circle (dark gray)
+      ctx.beginPath();
+      ctx.arc(centerX, centerY, radius, 0, Math.PI * 2);
+      ctx.fillStyle = '#3a3a3a';
+      ctx.fill();
+
+      // Draw progress pie (filled wedge)
+      const startAngle = -Math.PI / 2; // Start at top (12 o'clock)
+      const endAngle = startAngle + (percentage / 100) * Math.PI * 2;
+
+      if (percentage > 0) {
+        ctx.beginPath();
+        ctx.moveTo(centerX, centerY);
+        ctx.arc(centerX, centerY, radius, startAngle, endAngle);
+        ctx.closePath();
+
+        // Create gradient for progress pie
+        const gradient = ctx.createLinearGradient(0, 0, 128, 128);
+        gradient.addColorStop(0, startColor);
+        gradient.addColorStop(1, endColor);
+        ctx.fillStyle = gradient;
+        ctx.fill();
+      }
+
+      // Draw subtle border around the circle
+      ctx.beginPath();
+      ctx.arc(centerX, centerY, radius, 0, Math.PI * 2);
+      ctx.strokeStyle = 'rgba(0, 0, 0, 0.3)';
+      ctx.lineWidth = 2;
+      ctx.stroke();
+
+      // Draw percentage text (if enabled)
+      if (showText) {
+        ctx.fillStyle = '#ffffff';
+        ctx.font = 'bold 32px Arial';
+        ctx.textAlign = 'center';
+        ctx.textBaseline = 'middle';
+        ctx.shadowColor = 'rgba(0, 0, 0, 0.5)';
+        ctx.shadowBlur = 4;
+        ctx.shadowOffsetX = 1;
+        ctx.shadowOffsetY = 1;
+
+        const text = Math.round(percentage).toString() + '%';
+        ctx.fillText(text, centerX, centerY);
+      }
+
+      // Send back as data URL
+      ipcRenderer.send('icon-generated', canvas.toDataURL());
+    });
+  </script>
+</body>
+</html>
diff --git a/src/renderer/app.js b/src/renderer/app.js
index 9c81fb2..e0a585f 100644
--- a/src/renderer/app.js
+++ b/src/renderer/app.js
@@ -39,6 +39,10 @@ async function init() {
     const colorPrefs = await window.electronAPI.getColorPreferences();
     applyColorPreferences(colorPrefs);
 
+    // Load and apply theme settings
+    const themeSettings = await window.electronAPI.getThemeSettings();
+    applyThemePreferences(themeSettings);
+
     if (credentials.sessionKey && credentials.organizationId) {
         showMainContent();
         await fetchUsageData();
@@ -114,6 +118,12 @@ function setupEventListeners() {
         console.log('Colors changed, applying new preferences');
         applyColorPreferences(preferences);
     });
+
+    // Listen for theme changes from settings window
+    window.electronAPI.onThemeChanged((theme) => {
+        console.log('Theme changed, applying new theme');
+        applyThemePreferences(theme);
+    });
 }
 
 // Fetch usage data from Claude API
@@ -159,6 +169,11 @@ function hasNoUsage(data) {
 function updateUI(data) {
     latestUsageData = data;
 
+    // Send usage data to main process for tray icon
+    if (window.electronAPI && window.electronAPI.sendUsageToMain) {
+        window.electronAPI.sendUsageToMain(data);
+    }
+
     // Check if there's no usage data
     if (hasNoUsage(data)) {
         showNoUsage();
@@ -389,6 +404,36 @@ function applyColorPreferences(prefs) {
     root.style.setProperty('--color-danger-end', prefs.danger.end);
 }
 
+// Theme preference management
+function applyThemePreferences(theme) {
+    const root = document.documentElement;
+    const widgetContainer = document.querySelector('.widget-container');
+    const titleBar = document.querySelector('.title-bar');
+
+    // Apply background gradient
+    if (widgetContainer) {
+        widgetContainer.style.background = `linear-gradient(135deg, ${theme.backgroundStart} 0%, ${theme.backgroundEnd} 100%)`;
+    }
+
+    // Apply text colors
+    root.style.setProperty('--text-primary', theme.textPrimary);
+    root.style.setProperty('--text-secondary', theme.textSecondary);
+
+    // Apply title bar background
+    if (titleBar) {
+        const opacity = theme.titleBarOpacity / 100;
+        const bgColor = theme.titleBarBg;
+        titleBar.style.background = `rgba(${parseInt(bgColor.slice(1, 3), 16)}, ${parseInt(bgColor.slice(3, 5), 16)}, ${parseInt(bgColor.slice(5, 7), 16)}, ${opacity})`;
+    }
+
+    // Apply border color
+    if (widgetContainer) {
+        const borderOpacity = theme.borderOpacity / 100;
+        const borderColor = theme.borderColor;
+        widgetContainer.style.borderColor = `rgba(${parseInt(borderColor.slice(1, 3), 16)}, ${parseInt(borderColor.slice(3, 5), 16)}, ${parseInt(borderColor.slice(5, 7), 16)}, ${borderOpacity})`;
+    }
+}
+
 // Auto-update management
 function startAutoUpdate() {
     stopAutoUpdate();
diff --git a/src/renderer/settings-styles.css b/src/renderer/settings-styles.css
index defc2f5..b628c18 100644
--- a/src/renderer/settings-styles.css
+++ b/src/renderer/settings-styles.css
@@ -86,6 +86,8 @@ body {
     margin: 0 auto;
     padding: 24px;
     flex: 1;
+    overflow-y: auto;
+    max-height: calc(100vh - 36px); /* Account for title bar height */
 }
 
 .settings-section {
@@ -228,3 +230,309 @@ body {
 .disclaimer {
     margin-top: 16px;
 }
+
+/* Setting Groups */
+.setting-group {
+    margin-bottom: 25px;
+}
+
+.setting-group h3 {
+    font-size: 13px;
+    font-weight: 600;
+    margin-bottom: 8px;
+    color: #e5e7eb;
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+}
+
+.setting-description {
+    color: #9ca3af;
+    font-size: 12px;
+    margin-bottom: 12px;
+    line-height: 1.4;
+}
+
+/* Radio Buttons */
+.radio-group {
+    display: flex;
+    flex-direction: column;
+    gap: 10px;
+    margin-bottom: 20px;
+}
+
+.radio-item {
+    display: flex;
+    align-items: center;
+    gap: 12px;
+    padding: 12px;
+    border-radius: 8px;
+    border: 1px solid rgba(255, 255, 255, 0.1);
+    cursor: pointer;
+    transition: all 0.2s;
+    background: rgba(255, 255, 255, 0.03);
+}
+
+.radio-item:hover {
+    background: rgba(139, 92, 246, 0.1);
+    border-color: rgba(139, 92, 246, 0.3);
+}
+
+.radio-item input[type="radio"] {
+    width: 18px;
+    height: 18px;
+    cursor: pointer;
+    margin: 0;
+    flex-shrink: 0;
+    accent-color: #8b5cf6;
+}
+
+.radio-content {
+    display: flex;
+    flex-direction: column;
+    gap: 2px;
+}
+
+.radio-label {
+    font-weight: 500;
+    color: #e5e7eb;
+    font-size: 13px;
+}
+
+.radio-sublabel {
+    font-size: 11px;
+    color: #9ca3af;
+}
+
+/* Slider */
+.slider-container {
+    display: flex;
+    flex-direction: column;
+    gap: 10px;
+    margin-bottom: 20px;
+}
+
+.slider-container input[type="range"] {
+    width: 100%;
+    height: 6px;
+    border-radius: 3px;
+    background: rgba(255, 255, 255, 0.1);
+    outline: none;
+    -webkit-appearance: none;
+}
+
+.slider-container input[type="range"]::-webkit-slider-thumb {
+    -webkit-appearance: none;
+    appearance: none;
+    width: 18px;
+    height: 18px;
+    border-radius: 50%;
+    background: #8b5cf6;
+    cursor: pointer;
+    transition: background 0.2s;
+}
+
+.slider-container input[type="range"]::-webkit-slider-thumb:hover {
+    background: #a78bfa;
+}
+
+.slider-container input[type="range"]::-moz-range-thumb {
+    width: 18px;
+    height: 18px;
+    border-radius: 50%;
+    background: #8b5cf6;
+    cursor: pointer;
+    border: none;
+    transition: background 0.2s;
+}
+
+.slider-container input[type="range"]::-moz-range-thumb:hover {
+    background: #a78bfa;
+}
+
+.slider-value {
+    text-align: center;
+    font-size: 14px;
+    color: #e5e7eb;
+}
+
+.slider-value span {
+    font-weight: 600;
+    color: #8b5cf6;
+    font-size: 16px;
+}
+
+/* Toggle Switch */
+.toggle-switch {
+    display: flex;
+    align-items: center;
+    gap: 12px;
+    cursor: pointer;
+}
+
+.toggle-switch input[type="checkbox"] {
+    display: none;
+}
+
+.toggle-slider {
+    position: relative;
+    width: 48px;
+    height: 24px;
+    background: rgba(255, 255, 255, 0.1);
+    border-radius: 12px;
+    transition: background 0.3s;
+    flex-shrink: 0;
+}
+
+.toggle-slider::before {
+    content: '';
+    position: absolute;
+    width: 20px;
+    height: 20px;
+    border-radius: 50%;
+    background: #9ca3af;
+    top: 2px;
+    left: 2px;
+    transition: all 0.3s;
+}
+
+.toggle-switch input[type="checkbox"]:checked + .toggle-slider {
+    background: rgba(139, 92, 246, 0.3);
+}
+
+.toggle-switch input[type="checkbox"]:checked + .toggle-slider::before {
+    background: #8b5cf6;
+    transform: translateX(24px);
+}
+
+.toggle-label {
+    font-size: 13px;
+    color: #9ca3af;
+    transition: color 0.3s;
+}
+
+.toggle-switch input[type="checkbox"]:checked ~ .toggle-label {
+    color: #8b5cf6;
+}
+
+/* Custom Scrollbar */
+.settings-container::-webkit-scrollbar {
+    width: 8px;
+}
+
+.settings-container::-webkit-scrollbar-track {
+    background: rgba(255, 255, 255, 0.05);
+    border-radius: 4px;
+}
+
+.settings-container::-webkit-scrollbar-thumb {
+    background: rgba(139, 92, 246, 0.3);
+    border-radius: 4px;
+    transition: background 0.3s;
+}
+
+.settings-container::-webkit-scrollbar-thumb:hover {
+    background: rgba(139, 92, 246, 0.5);
+}
+
+/* Collapsible Sections */
+.collapsible-section {
+    margin-bottom: 16px;
+}
+
+.collapsible-header {
+    width: 100%;
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 12px 16px;
+    background: rgba(255, 255, 255, 0.05);
+    border: 1px solid rgba(255, 255, 255, 0.1);
+    border-radius: 8px;
+    cursor: pointer;
+    transition: all 0.2s;
+    color: #e5e7eb;
+    font-size: 13px;
+    font-weight: 600;
+}
+
+.collapsible-header:hover {
+    background: rgba(139, 92, 246, 0.1);
+    border-color: rgba(139, 92, 246, 0.3);
+}
+
+.collapsible-header span {
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+}
+
+.collapsible-header .chevron {
+    transition: transform 0.3s ease;
+    color: #9ca3af;
+}
+
+.collapsible-header.active .chevron {
+    transform: rotate(180deg);
+}
+
+.collapsible-content {
+    max-height: 0;
+    overflow: hidden;
+    transition: max-height 0.3s ease;
+    padding: 0 16px;
+}
+
+.collapsible-content.active {
+    max-height: 1000px;
+    padding: 16px;
+    padding-top: 16px;
+}
+
+/* Theme Grid */
+.theme-grid {
+    display: grid;
+    grid-template-columns: repeat(2, 1fr);
+    gap: 16px;
+    margin-bottom: 16px;
+}
+
+.theme-item {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    gap: 8px;
+}
+
+.theme-item label {
+    font-size: 11px;
+    font-weight: 600;
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+    color: #a0a0a0;
+    text-align: center;
+}
+
+.theme-item input[type="color"] {
+    width: 80px;
+    height: 50px;
+    border: 2px solid rgba(255, 255, 255, 0.2);
+    border-radius: 8px;
+    background: transparent;
+    cursor: pointer;
+    padding: 4px;
+    transition: all 0.2s ease;
+}
+
+.theme-item input[type="color"]:hover {
+    border-color: rgba(255, 255, 255, 0.4);
+    transform: translateY(-2px);
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
+}
+
+.theme-item input[type="color"]::-webkit-color-swatch-wrapper {
+    padding: 0;
+}
+
+.theme-item input[type="color"]::-webkit-color-swatch {
+    border: none;
+    border-radius: 6px;
+}
diff --git a/src/renderer/settings.html b/src/renderer/settings.html
index 3e72b72..2b0e60d 100644
--- a/src/renderer/settings.html
+++ b/src/renderer/settings.html
@@ -27,43 +27,249 @@
 
         <div class="settings-container">
 
-            <!-- Color Customization -->
+            <!-- Main Window Section -->
             <section class="settings-section">
-                <h2>Customize Colors</h2>
+                <h2>Main Window</h2>
 
-                <div class="color-grid-2col">
-                    <div class="color-item">
-                        <label>Normal Start</label>
-                        <input type="color" id="colorNormalStart" value="#8b5cf6">
-                    </div>
+                <!-- Collapsible Color Customization -->
+                <div class="collapsible-section">
+                    <button class="collapsible-header" id="mainWindowColorsHeader">
+                        <span>Colors</span>
+                        <svg class="chevron" width="16" height="16" viewBox="0 0 16 16" fill="none">
+                            <path d="M4 6L8 10L12 6" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+                        </svg>
+                    </button>
+                    <div class="collapsible-content" id="mainWindowColorsContent">
+                        <!-- Static Color Toggle -->
+                        <label class="toggle-switch" style="margin-bottom: 16px;">
+                            <input type="checkbox" id="mainWindowStaticColor">
+                            <span class="toggle-slider"></span>
+                            <span class="toggle-label">Use Static Color</span>
+                        </label>
 
-                    <div class="color-item">
-                        <label>Normal End</label>
-                        <input type="color" id="colorNormalEnd" value="#a78bfa">
-                    </div>
+                        <!-- Static Color Picker (shown when toggle is ON) -->
+                        <div id="mainWindowStaticColorPicker" style="display: none; margin-bottom: 16px;">
+                            <div class="color-item" style="width: 100%;">
+                                <label>Progress Bar Color</label>
+                                <input type="color" id="mainWindowStaticColorValue" value="#8b5cf6">
+                            </div>
+                        </div>
 
-                    <div class="color-item">
-                        <label>Warning Start</label>
-                        <input type="color" id="colorWarningStart" value="#f59e0b">
-                    </div>
+                        <!-- Gradient Color Pickers (shown when toggle is OFF) -->
+                        <div class="color-grid-2col" id="mainWindowGradientPickers">
+                            <div class="color-item">
+                                <label>Normal Start</label>
+                                <input type="color" id="colorNormalStart" value="#8b5cf6">
+                            </div>
 
-                    <div class="color-item">
-                        <label>Warning End</label>
-                        <input type="color" id="colorWarningEnd" value="#fbbf24">
-                    </div>
+                            <div class="color-item">
+                                <label>Normal End</label>
+                                <input type="color" id="colorNormalEnd" value="#a78bfa">
+                            </div>
 
-                    <div class="color-item">
-                        <label>Danger Start</label>
-                        <input type="color" id="colorDangerStart" value="#ef4444">
-                    </div>
+                            <div class="color-item">
+                                <label>Warning Start</label>
+                                <input type="color" id="colorWarningStart" value="#f59e0b">
+                            </div>
 
-                    <div class="color-item">
-                        <label>Danger End</label>
-                        <input type="color" id="colorDangerEnd" value="#f87171">
+                            <div class="color-item">
+                                <label>Warning End</label>
+                                <input type="color" id="colorWarningEnd" value="#fbbf24">
+                            </div>
+
+                            <div class="color-item">
+                                <label>Danger Start</label>
+                                <input type="color" id="colorDangerStart" value="#ef4444">
+                            </div>
+
+                            <div class="color-item">
+                                <label>Danger End</label>
+                                <input type="color" id="colorDangerEnd" value="#f87171">
+                            </div>
+                        </div>
+
+                        <button class="btn-secondary" id="resetColorsBtn">Reset to Defaults</button>
                     </div>
                 </div>
 
-                <button class="btn-secondary" id="resetColorsBtn">Reset to Defaults</button>
+                <!-- Theme Settings -->
+                <div class="collapsible-section">
+                    <button class="collapsible-header" id="mainWindowThemeHeader">
+                        <span>Theme</span>
+                        <svg class="chevron" width="16" height="16" viewBox="0 0 16 16" fill="none">
+                            <path d="M4 6L8 10L12 6" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+                        </svg>
+                    </button>
+                    <div class="collapsible-content" id="mainWindowThemeContent">
+                        <p class="setting-description">Customize the widget's overall appearance</p>
+
+                        <div class="theme-grid">
+                            <!-- Background Gradient -->
+                            <div class="theme-item">
+                                <label>Background Start</label>
+                                <input type="color" id="backgroundColorStart" value="#1e1e2e">
+                            </div>
+
+                            <div class="theme-item">
+                                <label>Background End</label>
+                                <input type="color" id="backgroundColorEnd" value="#2a2a3e">
+                            </div>
+
+                            <!-- Text Colors -->
+                            <div class="theme-item">
+                                <label>Primary Text</label>
+                                <input type="color" id="textColorPrimary" value="#e0e0e0">
+                            </div>
+
+                            <div class="theme-item">
+                                <label>Secondary Text</label>
+                                <input type="color" id="textColorSecondary" value="#a0a0a0">
+                            </div>
+
+                            <!-- UI Elements -->
+                            <div class="theme-item">
+                                <label>Title Bar Background</label>
+                                <input type="color" id="titleBarBackground" value="#000000">
+                                <input type="range" id="titleBarOpacity" min="0" max="100" value="30" style="width: 100%; margin-top: 4px;">
+                                <div style="text-align: center; font-size: 10px; color: #9ca3af; margin-top: 2px;">
+                                    Opacity: <span id="titleBarOpacityValue">30</span>%
+                                </div>
+                            </div>
+
+                            <div class="theme-item">
+                                <label>Border Color</label>
+                                <input type="color" id="borderColor" value="#ffffff">
+                                <input type="range" id="borderOpacity" min="0" max="100" value="10" style="width: 100%; margin-top: 4px;">
+                                <div style="text-align: center; font-size: 10px; color: #9ca3af; margin-top: 2px;">
+                                    Opacity: <span id="borderOpacityValue">10</span>%
+                                </div>
+                            </div>
+                        </div>
+
+                        <button class="btn-secondary" id="resetThemeBtn">Reset Theme</button>
+                    </div>
+                </div>
+            </section>
+
+            <div class="divider"></div>
+
+            <!-- Tray Icon Settings -->
+            <section class="settings-section">
+                <h2>Tray Icon</h2>
+
+                <!-- Display Mode -->
+                <div class="setting-group">
+                    <h3>Display Mode</h3>
+                    <p class="setting-description">Choose which usage metric to display in the system tray</p>
+
+                    <div class="radio-group">
+                        <label class="radio-item">
+                            <input type="radio" name="trayDisplay" value="session" id="trayDisplaySession" checked>
+                            <div class="radio-content">
+                                <span class="radio-label">Session Usage</span>
+                                <span class="radio-sublabel">5-hour limit</span>
+                            </div>
+                        </label>
+
+                        <label class="radio-item">
+                            <input type="radio" name="trayDisplay" value="weekly" id="trayDisplayWeekly">
+                            <div class="radio-content">
+                                <span class="radio-label">Weekly Usage</span>
+                                <span class="radio-sublabel">7-day limit</span>
+                            </div>
+                        </label>
+                    </div>
+                </div>
+
+                <!-- Update Interval -->
+                <div class="setting-group">
+                    <h3>Update Interval</h3>
+                    <p class="setting-description">How often to refresh the tray icon (in seconds)</p>
+
+                    <div class="slider-container">
+                        <input type="range" id="trayUpdateInterval" min="10" max="300" value="30" step="10">
+                        <div class="slider-value">
+                            <span id="trayUpdateValue">30</span> seconds
+                        </div>
+                    </div>
+                </div>
+
+                <!-- Show Text Toggle -->
+                <div class="setting-group">
+                    <h3>Show Percentage Text</h3>
+                    <p class="setting-description">Display percentage number on the tray icon</p>
+
+                    <label class="toggle-switch">
+                        <input type="checkbox" id="trayShowText" checked>
+                        <span class="toggle-slider"></span>
+                        <span class="toggle-label" id="trayShowTextLabel">Enabled</span>
+                    </label>
+                </div>
+
+                <!-- Tray Icon Colors -->
+                <div class="setting-group">
+                    <div class="collapsible-section">
+                        <button class="collapsible-header" id="trayColorsHeader">
+                            <span>Colors</span>
+                            <svg class="chevron" width="16" height="16" viewBox="0 0 16 16" fill="none">
+                                <path d="M4 6L8 10L12 6" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+                            </svg>
+                        </button>
+                        <div class="collapsible-content" id="trayColorsContent">
+                            <p class="setting-description">Customize colors for the tray icon progress indicator</p>
+
+                            <!-- Static Color Toggle -->
+                            <label class="toggle-switch" style="margin-bottom: 16px;">
+                                <input type="checkbox" id="trayStaticColor">
+                                <span class="toggle-slider"></span>
+                                <span class="toggle-label">Use Static Color</span>
+                            </label>
+
+                            <!-- Static Color Picker (shown when toggle is ON) -->
+                            <div id="trayStaticColorPicker" style="display: none; margin-bottom: 16px;">
+                                <div class="color-item" style="width: 100%;">
+                                    <label>Tray Icon Color</label>
+                                    <input type="color" id="trayStaticColorValue" value="#8b5cf6">
+                                </div>
+                            </div>
+
+                            <!-- Gradient Color Pickers (shown when toggle is OFF) -->
+                            <div class="color-grid-2col" id="trayGradientPickers">
+                                <div class="color-item">
+                                    <label>Normal Start</label>
+                                    <input type="color" id="trayColorNormalStart" value="#8b5cf6">
+                                </div>
+
+                                <div class="color-item">
+                                    <label>Normal End</label>
+                                    <input type="color" id="trayColorNormalEnd" value="#a78bfa">
+                                </div>
+
+                                <div class="color-item">
+                                    <label>Warning Start</label>
+                                    <input type="color" id="trayColorWarningStart" value="#f59e0b">
+                                </div>
+
+                                <div class="color-item">
+                                    <label>Warning End</label>
+                                    <input type="color" id="trayColorWarningEnd" value="#fbbf24">
+                                </div>
+
+                                <div class="color-item">
+                                    <label>Danger Start</label>
+                                    <input type="color" id="trayColorDangerStart" value="#ef4444">
+                                </div>
+
+                                <div class="color-item">
+                                    <label>Danger End</label>
+                                    <input type="color" id="trayColorDangerEnd" value="#f87171">
+                                </div>
+                            </div>
+
+                            <button class="btn-secondary" id="resetTrayColorsBtn">Reset Tray Colors</button>
+                        </div>
+                    </div>
+                </div>
             </section>
 
             <div class="divider"></div>
diff --git a/src/renderer/settings.js b/src/renderer/settings.js
index e48fe9b..f4b73d6 100644
--- a/src/renderer/settings.js
+++ b/src/renderer/settings.js
@@ -10,16 +10,72 @@ const elements = {
     logoutBtn: document.getElementById('logoutBtn'),
     coffeeBtn: document.getElementById('coffeeBtn'),
     minimizeBtn: document.getElementById('minimizeBtn'),
-    closeBtn: document.getElementById('closeBtn')
+    closeBtn: document.getElementById('closeBtn'),
+    // Tray icon elements
+    trayDisplaySession: document.getElementById('trayDisplaySession'),
+    trayDisplayWeekly: document.getElementById('trayDisplayWeekly'),
+    trayUpdateInterval: document.getElementById('trayUpdateInterval'),
+    trayUpdateValue: document.getElementById('trayUpdateValue'),
+    trayShowText: document.getElementById('trayShowText'),
+    trayShowTextLabel: document.getElementById('trayShowTextLabel'),
+    trayColorNormalStart: document.getElementById('trayColorNormalStart'),
+    trayColorNormalEnd: document.getElementById('trayColorNormalEnd'),
+    trayColorWarningStart: document.getElementById('trayColorWarningStart'),
+    trayColorWarningEnd: document.getElementById('trayColorWarningEnd'),
+    trayColorDangerStart: document.getElementById('trayColorDangerStart'),
+    trayColorDangerEnd: document.getElementById('trayColorDangerEnd'),
+    resetTrayColorsBtn: document.getElementById('resetTrayColorsBtn'),
+    // Static color toggles
+    mainWindowStaticColor: document.getElementById('mainWindowStaticColor'),
+    mainWindowStaticColorPicker: document.getElementById('mainWindowStaticColorPicker'),
+    mainWindowStaticColorValue: document.getElementById('mainWindowStaticColorValue'),
+    mainWindowGradientPickers: document.getElementById('mainWindowGradientPickers'),
+    trayStaticColor: document.getElementById('trayStaticColor'),
+    trayStaticColorPicker: document.getElementById('trayStaticColorPicker'),
+    trayStaticColorValue: document.getElementById('trayStaticColorValue'),
+    trayGradientPickers: document.getElementById('trayGradientPickers'),
+    // Theme elements
+    backgroundColorStart: document.getElementById('backgroundColorStart'),
+    backgroundColorEnd: document.getElementById('backgroundColorEnd'),
+    textColorPrimary: document.getElementById('textColorPrimary'),
+    textColorSecondary: document.getElementById('textColorSecondary'),
+    titleBarBackground: document.getElementById('titleBarBackground'),
+    titleBarOpacity: document.getElementById('titleBarOpacity'),
+    titleBarOpacityValue: document.getElementById('titleBarOpacityValue'),
+    borderColor: document.getElementById('borderColor'),
+    borderOpacity: document.getElementById('borderOpacity'),
+    borderOpacityValue: document.getElementById('borderOpacityValue'),
+    resetThemeBtn: document.getElementById('resetThemeBtn')
 };
 
 // Initialize
 async function init() {
     setupEventListeners();
+    setupCollapsibleSections();
 
     // Load and apply color preferences
     const colorPrefs = await window.electronAPI.getColorPreferences();
     loadColorPickerValues(colorPrefs);
+
+    // Load and apply tray settings
+    const traySettings = await window.electronAPI.getTraySettings();
+    loadTraySettings(traySettings);
+
+    // Load tray update interval
+    const interval = await window.electronAPI.getTrayUpdateInterval();
+    loadTrayUpdateInterval(interval);
+
+    // Load theme settings
+    await loadThemeSettings();
+
+    // Apply theme to settings window
+    const theme = await window.electronAPI.getThemeSettings();
+    applyThemeToSettings(theme);
+
+    // Listen for theme changes
+    window.electronAPI.onThemeChanged((theme) => {
+        applyThemeToSettings(theme);
+    });
 }
 
 // Event Listeners
@@ -70,38 +126,358 @@ function setupEventListeners() {
     elements.closeBtn.addEventListener('click', () => {
         window.close();
     });
+
+    // Tray icon event listeners
+    elements.trayDisplaySession.addEventListener('change', saveTraySettings);
+    elements.trayDisplayWeekly.addEventListener('change', saveTraySettings);
+
+    elements.trayShowText.addEventListener('change', () => {
+        elements.trayShowTextLabel.textContent = elements.trayShowText.checked ? 'Enabled' : 'Disabled';
+        saveTraySettings();
+    });
+
+    const trayColorInputs = [
+        elements.trayColorNormalStart,
+        elements.trayColorNormalEnd,
+        elements.trayColorWarningStart,
+        elements.trayColorWarningEnd,
+        elements.trayColorDangerStart,
+        elements.trayColorDangerEnd
+    ];
+
+    trayColorInputs.forEach(input => {
+        input.addEventListener('change', saveTraySettings);
+    });
+
+    elements.trayUpdateInterval.addEventListener('input', () => {
+        elements.trayUpdateValue.textContent = elements.trayUpdateInterval.value;
+    });
+
+    elements.trayUpdateInterval.addEventListener('change', () => {
+        window.electronAPI.setTrayUpdateInterval(parseInt(elements.trayUpdateInterval.value));
+    });
+
+    elements.resetTrayColorsBtn.addEventListener('click', async () => {
+        const defaults = {
+            displayMode: elements.trayDisplaySession.checked ? 'session' : 'weekly',
+            showText: false,
+            colors: {
+                normal: { start: '#8b5cf6', end: '#a78bfa' },
+                warning: { start: '#f59e0b', end: '#fbbf24' },
+                danger: { start: '#ef4444', end: '#f87171' }
+            }
+        };
+        await window.electronAPI.setTraySettings(defaults);
+        loadTraySettings(defaults);
+    });
+
+    // Main Window static color toggle
+    elements.mainWindowStaticColor.addEventListener('change', () => {
+        const isStatic = elements.mainWindowStaticColor.checked;
+        elements.mainWindowStaticColorPicker.style.display = isStatic ? 'block' : 'none';
+        elements.mainWindowGradientPickers.style.display = isStatic ? 'none' : 'grid';
+        saveCurrentColors();
+    });
+
+    elements.mainWindowStaticColorValue.addEventListener('change', saveCurrentColors);
+
+    // Tray static color toggle
+    elements.trayStaticColor.addEventListener('change', () => {
+        const isStatic = elements.trayStaticColor.checked;
+        elements.trayStaticColorPicker.style.display = isStatic ? 'block' : 'none';
+        elements.trayGradientPickers.style.display = isStatic ? 'none' : 'grid';
+        saveTraySettings();
+    });
+
+    elements.trayStaticColorValue.addEventListener('change', saveTraySettings);
+
+    // Theme settings
+    const themeInputs = [
+        elements.backgroundColorStart,
+        elements.backgroundColorEnd,
+        elements.textColorPrimary,
+        elements.textColorSecondary,
+        elements.titleBarBackground,
+        elements.borderColor
+    ];
+
+    themeInputs.forEach(input => {
+        input.addEventListener('change', saveThemeSettings);
+    });
+
+    // Opacity sliders
+    elements.titleBarOpacity.addEventListener('input', () => {
+        elements.titleBarOpacityValue.textContent = elements.titleBarOpacity.value;
+    });
+
+    elements.titleBarOpacity.addEventListener('change', saveThemeSettings);
+
+    elements.borderOpacity.addEventListener('input', () => {
+        elements.borderOpacityValue.textContent = elements.borderOpacity.value;
+    });
+
+    elements.borderOpacity.addEventListener('change', saveThemeSettings);
+
+    // Reset theme button
+    elements.resetThemeBtn.addEventListener('click', resetTheme);
 }
 
 // Helper functions
 function loadColorPickerValues(prefs) {
-    elements.colorNormalStart.value = prefs.normal.start;
-    elements.colorNormalEnd.value = prefs.normal.end;
-    elements.colorWarningStart.value = prefs.warning.start;
-    elements.colorWarningEnd.value = prefs.warning.end;
-    elements.colorDangerStart.value = prefs.danger.start;
-    elements.colorDangerEnd.value = prefs.danger.end;
+    // Check if static mode
+    const isStatic = prefs.isStatic || false;
+    elements.mainWindowStaticColor.checked = isStatic;
+
+    if (isStatic) {
+        // Load static color
+        elements.mainWindowStaticColorValue.value = prefs.staticColor || '#8b5cf6';
+        elements.mainWindowStaticColorPicker.style.display = 'block';
+        elements.mainWindowGradientPickers.style.display = 'none';
+    } else {
+        // Load gradient colors
+        elements.colorNormalStart.value = prefs.normal.start;
+        elements.colorNormalEnd.value = prefs.normal.end;
+        elements.colorWarningStart.value = prefs.warning.start;
+        elements.colorWarningEnd.value = prefs.warning.end;
+        elements.colorDangerStart.value = prefs.danger.start;
+        elements.colorDangerEnd.value = prefs.danger.end;
+        elements.mainWindowStaticColorPicker.style.display = 'none';
+        elements.mainWindowGradientPickers.style.display = 'grid';
+    }
 }
 
 async function saveCurrentColors() {
-    const prefs = {
-        normal: {
-            start: elements.colorNormalStart.value,
-            end: elements.colorNormalEnd.value
-        },
-        warning: {
-            start: elements.colorWarningStart.value,
-            end: elements.colorWarningEnd.value
-        },
-        danger: {
-            start: elements.colorDangerStart.value,
-            end: elements.colorDangerEnd.value
-        }
-    };
+    const isStatic = elements.mainWindowStaticColor.checked;
+
+    let prefs;
+    if (isStatic) {
+        // Use static color for all states
+        const staticColor = elements.mainWindowStaticColorValue.value;
+        prefs = {
+            isStatic: true,
+            staticColor: staticColor,
+            normal: { start: staticColor, end: staticColor },
+            warning: { start: staticColor, end: staticColor },
+            danger: { start: staticColor, end: staticColor }
+        };
+    } else {
+        // Use gradient colors
+        prefs = {
+            isStatic: false,
+            normal: {
+                start: elements.colorNormalStart.value,
+                end: elements.colorNormalEnd.value
+            },
+            warning: {
+                start: elements.colorWarningStart.value,
+                end: elements.colorWarningEnd.value
+            },
+            danger: {
+                start: elements.colorDangerStart.value,
+                end: elements.colorDangerEnd.value
+            }
+        };
+    }
 
     await window.electronAPI.setColorPreferences(prefs);
     // Notify main window to update colors
     await window.electronAPI.notifyColorChange(prefs);
 }
 
+// Tray settings functions
+function loadTraySettings(settings) {
+    // Set display mode
+    if (settings.displayMode === 'weekly') {
+        elements.trayDisplayWeekly.checked = true;
+    } else {
+        elements.trayDisplaySession.checked = true;
+    }
+
+    // Set show text toggle
+    const showText = settings.showText !== undefined ? settings.showText : false;
+    elements.trayShowText.checked = showText;
+    elements.trayShowTextLabel.textContent = showText ? 'Enabled' : 'Disabled';
+
+    // Check if static mode
+    const isStatic = settings.isStatic || false;
+    elements.trayStaticColor.checked = isStatic;
+
+    if (isStatic) {
+        // Load static color
+        elements.trayStaticColorValue.value = settings.staticColor || '#8b5cf6';
+        elements.trayStaticColorPicker.style.display = 'block';
+        elements.trayGradientPickers.style.display = 'none';
+    } else {
+        // Load gradient colors
+        elements.trayColorNormalStart.value = settings.colors.normal.start;
+        elements.trayColorNormalEnd.value = settings.colors.normal.end;
+        elements.trayColorWarningStart.value = settings.colors.warning.start;
+        elements.trayColorWarningEnd.value = settings.colors.warning.end;
+        elements.trayColorDangerStart.value = settings.colors.danger.start;
+        elements.trayColorDangerEnd.value = settings.colors.danger.end;
+        elements.trayStaticColorPicker.style.display = 'none';
+        elements.trayGradientPickers.style.display = 'grid';
+    }
+}
+
+function loadTrayUpdateInterval(interval) {
+    elements.trayUpdateInterval.value = interval;
+    elements.trayUpdateValue.textContent = interval;
+}
+
+async function saveTraySettings() {
+    const isStatic = elements.trayStaticColor.checked;
+
+    let settings;
+    if (isStatic) {
+        // Use static color for all states
+        const staticColor = elements.trayStaticColorValue.value;
+        settings = {
+            displayMode: elements.trayDisplayWeekly.checked ? 'weekly' : 'session',
+            showText: elements.trayShowText.checked,
+            isStatic: true,
+            staticColor: staticColor,
+            colors: {
+                normal: { start: staticColor, end: staticColor },
+                warning: { start: staticColor, end: staticColor },
+                danger: { start: staticColor, end: staticColor }
+            }
+        };
+    } else {
+        // Use gradient colors
+        settings = {
+            displayMode: elements.trayDisplayWeekly.checked ? 'weekly' : 'session',
+            showText: elements.trayShowText.checked,
+            isStatic: false,
+            colors: {
+                normal: {
+                    start: elements.trayColorNormalStart.value,
+                    end: elements.trayColorNormalEnd.value
+                },
+                warning: {
+                    start: elements.trayColorWarningStart.value,
+                    end: elements.trayColorWarningEnd.value
+                },
+                danger: {
+                    start: elements.trayColorDangerStart.value,
+                    end: elements.trayColorDangerEnd.value
+                }
+            }
+        };
+    }
+
+    await window.electronAPI.setTraySettings(settings);
+}
+
+// Theme settings functions
+async function loadThemeSettings() {
+    const theme = await window.electronAPI.getThemeSettings();
+
+    elements.backgroundColorStart.value = theme.backgroundStart || '#1e1e2e';
+    elements.backgroundColorEnd.value = theme.backgroundEnd || '#2a2a3e';
+    elements.textColorPrimary.value = theme.textPrimary || '#e0e0e0';
+    elements.textColorSecondary.value = theme.textSecondary || '#a0a0a0';
+    elements.titleBarBackground.value = theme.titleBarBg || '#000000';
+    elements.titleBarOpacity.value = theme.titleBarOpacity || 30;
+    elements.titleBarOpacityValue.textContent = elements.titleBarOpacity.value;
+    elements.borderColor.value = theme.borderColor || '#ffffff';
+    elements.borderOpacity.value = theme.borderOpacity || 10;
+    elements.borderOpacityValue.textContent = elements.borderOpacity.value;
+}
+
+async function saveThemeSettings() {
+    const theme = {
+        backgroundStart: elements.backgroundColorStart.value,
+        backgroundEnd: elements.backgroundColorEnd.value,
+        textPrimary: elements.textColorPrimary.value,
+        textSecondary: elements.textColorSecondary.value,
+        titleBarBg: elements.titleBarBackground.value,
+        titleBarOpacity: parseInt(elements.titleBarOpacity.value),
+        borderColor: elements.borderColor.value,
+        borderOpacity: parseInt(elements.borderOpacity.value)
+    };
+
+    await window.electronAPI.setThemeSettings(theme);
+
+    // Apply theme to settings window immediately
+    applyThemeToSettings(theme);
+
+    // Notify main window to update
+    await window.electronAPI.notifyThemeChange(theme);
+}
+
+async function resetTheme() {
+    const defaults = {
+        backgroundStart: '#1e1e2e',
+        backgroundEnd: '#2a2a3e',
+        textPrimary: '#e0e0e0',
+        textSecondary: '#a0a0a0',
+        titleBarBg: '#000000',
+        titleBarOpacity: 30,
+        borderColor: '#ffffff',
+        borderOpacity: 10
+    };
+
+    await window.electronAPI.setThemeSettings(defaults);
+    await loadThemeSettings();
+
+    // Apply theme to settings window immediately
+    applyThemeToSettings(defaults);
+
+    // Notify main window to update
+    await window.electronAPI.notifyThemeChange(defaults);
+}
+
+// Apply theme to settings window
+function applyThemeToSettings(theme) {
+    const settingsApp = document.getElementById('settings-app');
+    const titleBar = document.querySelector('.title-bar');
+
+    // Apply background gradient
+    if (settingsApp) {
+        settingsApp.style.background = `linear-gradient(135deg, ${theme.backgroundStart} 0%, ${theme.backgroundEnd} 100%)`;
+    }
+
+    // Apply title bar background
+    if (titleBar) {
+        const opacity = theme.titleBarOpacity / 100;
+        const bgColor = theme.titleBarBg;
+        titleBar.style.background = `rgba(${parseInt(bgColor.slice(1, 3), 16)}, ${parseInt(bgColor.slice(3, 5), 16)}, ${parseInt(bgColor.slice(5, 7), 16)}, ${opacity})`;
+    }
+
+    // Apply text colors via CSS variables
+    const root = document.documentElement;
+    root.style.setProperty('--text-primary', theme.textPrimary);
+    root.style.setProperty('--text-secondary', theme.textSecondary);
+
+    // Update primary text color (titles, labels)
+    const primaryTextElements = document.querySelectorAll('.title span, h2, h3, .radio-label, .toggle-label, .setting-description');
+    primaryTextElements.forEach(el => {
+        if (el.classList.contains('setting-description')) {
+            // Secondary text for descriptions
+            el.style.color = theme.textSecondary;
+        } else {
+            // Primary text for titles/labels
+            el.style.color = theme.textPrimary;
+        }
+    });
+}
+
+// Setup collapsible sections
+function setupCollapsibleSections() {
+    const collapsibleHeaders = document.querySelectorAll('.collapsible-header');
+
+    collapsibleHeaders.forEach(header => {
+        header.addEventListener('click', () => {
+            const content = header.nextElementSibling;
+            const isActive = header.classList.contains('active');
+
+            // Toggle active state
+            header.classList.toggle('active');
+            content.classList.toggle('active');
+        });
+    });
+}
+
 // Start the application
 init();