:root {
  --bg: #050816;
  --card: #111827;
  --text: #f9fafb;
  --muted: #9ca3af;
  --accent: #4f46e5;
  --radius: 14px;
}

body {
  margin: 0;
  font-family: system-ui, sans-serif;
  background: #020617;
  color: var(--text);
}

.header {
  padding: 1rem 6vw;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: rgba(2, 6, 23, 0.9);
  border-bottom: 1px solid rgba(148, 163, 184, 0.2);
}

.logo {
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.nav a {
  margin-left: 1.5rem;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9rem;
}

.nav a:hover {
  color: var(--text);
}

.course-container {
  padding: 2rem 6vw;
}

.course-title {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.course-subtitle {
  color: var(--muted);
  margin-bottom: 2rem;
}

.lessons-list {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.lesson-card {
  background: var(--card);
  padding: 1.5rem;
  border-radius: var(--radius);
  border: 1px solid rgba(148, 163, 184, 0.25);
}

.lesson-card h2 {
  margin-top: 0;
}

.video-wrapper {
  margin: 1rem 0;
}

video {
  width: 100%;
  border-radius: var(--radius);
  background: #000;
}

.description-box {
  width: 100%;
  min-height: 100px;
  border-radius: var(--radius);
  border: 1px solid rgba(148, 163, 184, 0.3);
  background: rgba(15, 23, 42, 0.9);
  color: var(--text);
  padding: 0.8rem;
  font-size: 0.9rem;
  resize: vertical;
}

.footer {
  text-align: center;
  padding: 1.5rem;
  color: var(--muted);
  border-top: 1px solid rgba(148, 163, 184, 0.2);
}