* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', sans-serif;
}

body {
  background: linear-gradient(135deg, #eef2f7, #d9e4f5);
}

/* Header */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: linear-gradient(90deg, #4a90e2, #0077ff);
  color: white;
  padding: 15px 20px;
}

header h1 {
  font-size: 20px;
}

/* Dropdown */
.dropdown {
  position: relative;
}

.dropbtn {
  background: white;
  color: #0077ff;
  padding: 10px 14px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  font-size: 18px;
}

.dropdown-content {
  display: none;
  position: absolute;
  right: 0;
  top: 45px;
  background: white;
  border-radius: 10px;
  min-width: 180px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.15);
}

.dropdown-content a {
  display: block;
  padding: 12px;
  text-decoration: none;
  color: black;
}

.dropdown-content a:hover {
  background: #0077ff;
  color: white;
}

.show {
  display: block;
}

/* Layout */
.container {
  display: flex;
  gap: 20px;
  padding: 20px;
}

/* Sidebar */
.sidebar {
  width: 25%;
  background: white;
  padding: 15px;
  border-radius: 12px;
}

.sidebar h2 {
  margin-bottom: 10px;
  color: #0077ff;
}

.sidebar li {
  list-style: none;
  padding: 10px;
  margin-bottom: 8px;
  border-radius: 6px;
  cursor: pointer;
}

.sidebar li:hover {
  background: #f0f7ff;
}

.sidebar li.active {
  background: #0077ff;
  color: white;
}

/* Video Area */
.video-area {
  width: 75%;
  background: white;
  padding: 15px;
  border-radius: 12px;
}

video {
  width: 100%;
  border-radius: 10px;
}

#completeBtn {
  margin-top: 10px;
  padding: 10px;
  background: #00c853;
  color: white;
  border: none;
  border-radius: 6px;
  cursor: pointer;
}

#completeBtn:hover {
  background: #00e676;
}

#progressText {
  margin-top: 10px;
  font-weight: bold;
}

/* Mobile */
@media (max-width: 768px) {
  .container {
    flex-direction: column;
  }

  .sidebar,
  .video-area {
    width: 100%;
  }

  header h1 {
    font-size: 16px;
  }
}