body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: #1c1c2e;
  color: #fff;
  display: flex;
  transition: background 0.3s, color 0.3s;
}

body.light-mode {
  background: #f4f4f9;
  color: #333;
}

/* Sidebar Navigation */
.sidebar {
  width: 220px;
  background: #111;
  height: 100vh;
  padding: 20px;
  box-sizing: border-box;
}
.sidebar h2 { color: #fff; margin-bottom: 20px; }
.nav-btn, .sub-btn {
  width: 100%;
  background: none;
  border: none;
  color: #aaa;
  padding: 12px;
  text-align: left;
  font-size: 16px;
  cursor: pointer;
}
.nav-btn:hover, .sub-btn:hover, .active {
  color: #fff;
  background: #333;
}
.sub-menu {
  display: none;
  padding-left: 15px;
}
.sub-menu.open { 
  display: block; 
}

/* Main Content Components */
.content { flex: 1; padding: 30px; height: 100vh; overflow-y: auto; }
.page { display: none; }
.page.active { display: block; }
.card {
  background: rgba(255,255,255,0.05);
  padding: 20px;
  margin-bottom: 20px;
  border-radius: 8px;
}
body.light-mode .card { background: rgba(0,0,0,0.05); }

/* Form UI elements */
input, textarea {
  padding: 8px;
  margin-right: 5px;
  border-radius: 4px;
  border: 1px solid #555;
  background: #222;
  color: #fff;
}
body.light-mode input, body.light-mode textarea {
  background: #fff;
  color: #333;
  border: 1px solid #ccc;
}
button {
  padding: 8px 15px;
  background: #007bff;
  color: white;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}
button:hover { background: #0056b3; }

/* Interactive Task List */
ul { padding-left: 20px; }
li { cursor: pointer; margin: 5px 0; }
li.done { text-decoration: line-through; color: #888; }

/* Toast Notifications */
#toast {
  visibility: hidden;
  min-width: 250px;
  background-color: #333;
  color: #fff;
  text-align: center;
  border-radius: 4px;
  padding: 16px;
  position: fixed;
  z-index: 1000;
  right: 30px;
  top: 30px;
  font-size: 15px;
  white-space: pre-wrap;
  box-shadow: 0 4px 10px rgba(0,0,0,0.3);
}
#toast.show { visibility: visible; }
#toast.success { background-color: #2b8a3e; }
#toast.error { background-color: #c92a2a; }