@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;700&display=swap');

:root {
  --bg-dark: #020617;
  --bg-main: #0f172a;
  --primary: #38bdf8;
  --border: #1e293b;
  --text-soft: #94a3b8;
}

* {
  box-sizing: border-box;
  font-family: 'Inter', sans-serif;
}

body {
  margin: 0;
  background: radial-gradient(circle at top, #020617, #020617);
  color: #e5e7eb;
}

/* ===== Navbar ===== */
.navbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 18px 60px;
  background: rgba(2, 6, 23, 0.7);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.logo {
  font-size: 26px;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: 0.5px;
}

nav a {
  margin-left: 22px;
  color: #e5e7eb;
  transition: all 0.3s ease;
}

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

/* ===== Hero ===== */
.hero {
  padding: 120px 60px;
  background:
    radial-gradient(600px circle at 20% 10%, rgba(56,189,248,0.15), transparent),
    radial-gradient(600px circle at 80% 80%, rgba(14,165,233,0.12), transparent);
  animation: fadeUp 1s ease forwards;
}

.hero h1 {
  font-size: 60px;
  line-height: 1.1;
  margin-bottom: 20px;
}

.hero p {
  max-width: 520px;
  color: var(--text-soft);
  font-size: 18px;
}

/* ===== Section ===== */
.section {
  padding: 90px 60px;
}

.section h2 {
  font-size: 36px;
  margin-bottom: 40px;
}

.section.dark {
  background: linear-gradient(180deg, #020617, #020617);
}

/* ===== Cards ===== */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.card {
  background: rgba(2, 6, 23, 0.8);
  border: 1px solid var(--border);
  padding: 32px;
  border-radius: 18px;
  transition: all 0.35s ease;
  transform: translateY(0);
}

.card:hover {
  transform: translateY(-10px) scale(1.02);
  border-color: var(--primary);
  box-shadow: 0 20px 40px rgba(56,189,248,0.15);
}

.card h3 {
  margin-top: 0;
  font-size: 22px;
}

/* ===== Buttons ===== */
.btn {
  background: linear-gradient(135deg, #38bdf8, #0ea5e9);
  color: #020617;
  padding: 12px 26px;
  border-radius: 12px;
  font-weight: 600;
  display: inline-block;
  transition: all 0.3s ease;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 25px rgba(56,189,248,0.4);
}

.btn-outline {
  border: 1px solid var(--primary);
  padding: 10px 22px;
  border-radius: 12px;
  transition: all 0.3s ease;
}

.btn-outline:hover {
  background: var(--primary);
  color: #020617;
}

.big { font-size: 18px; }
.small { margin-top: 14px; }
.full { width: 100%; }

/* ===== Auth ===== */
.auth {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background:
    radial-gradient(600px circle at top, rgba(56,189,248,0.15), transparent),
    #020617;
}

.auth-box {
  background: rgba(2, 6, 23, 0.85);
  padding: 44px;
  border-radius: 20px;
  width: 340px;
  border: 1px solid var(--border);
  animation: fadeUp 0.8s ease forwards;
}

.auth-box h2 {
  margin-bottom: 20px;
}

.auth-box input {
  width: 100%;
  padding: 14px;
  margin: 10px 0;
  background: var(--bg-main);
  border: 1px solid var(--border);
  color: white;
  border-radius: 10px;
}

.auth-box input:focus {
  outline: none;
  border-color: var(--primary);
}

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 30px;
  color: var(--text-soft);
  font-size: 14px;
}

/* ===== Animations ===== */
@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
/* ===== Lesson Page ===== */

.lesson-layout {
  display: flex;
  min-height: calc(100vh - 80px);
}

.lesson-sidebar {
  width: 280px;
  background: rgba(2, 6, 23, 0.9);
  border-right: 1px solid var(--border);
  padding: 30px;
}

.lesson-sidebar h3 {
  margin-top: 0;
  margin-bottom: 20px;
  font-size: 18px;
}

.lesson-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.lesson-list li {
  padding: 12px;
  border-radius: 10px;
  margin-bottom: 10px;
  font-size: 14px;
  cursor: pointer;
  transition: all 0.3s ease;
}

.lesson-list li:hover {
  background: rgba(56,189,248,0.15);
}

.lesson-list li.active {
  background: rgba(56,189,248,0.25);
  color: #38bdf8;
}

.lesson-list li.locked {
  opacity: 0.5;
  cursor: not-allowed;
}

.lesson-content {
  flex: 1;
  padding: 50px 60px;
}

.progress {
  width: 100%;
  height: 8px;
  background: #1e293b;
  border-radius: 20px;
  overflow: hidden;
  margin: 20px 0 8px;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(135deg, #38bdf8, #0ea5e9);
}

.progress-text {
  font-size: 13px;
  color: var(--text-soft);
}

.video-box {
  margin: 30px 0;
}

.video-placeholder {
  height: 360px;
  background: linear-gradient(135deg, #020617, #020617);
  border: 1px solid var(--border);
  border-radius: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  color: var(--text-soft);
}

.lesson-text {
  max-width: 700px;
}

.lesson-actions {
  display: flex;
  justify-content: space-between;
  margin-top: 40px;
}
/* ===== Course Detail Page ===== */

.course-hero {
  padding: 100px 60px;
  background:
    radial-gradient(600px circle at 20% 20%, rgba(56,189,248,0.15), transparent),
    #020617;
}

.course-info {
  max-width: 720px;
  animation: fadeUp 0.8s ease forwards;
}

.course-info h1 {
  font-size: 48px;
  margin-bottom: 16px;
}

.subtitle {
  font-size: 18px;
  color: var(--text-soft);
  margin-bottom: 24px;
}

.course-meta {
  display: flex;
  gap: 20px;
  margin-bottom: 32px;
  color: var(--text-soft);
  font-size: 14px;
}

/* ===== Syllabus ===== */

.syllabus {
  max-width: 800px;
}

.lesson {
  display: flex;
  gap: 20px;
  padding: 20px;
  border-radius: 14px;
  border: 1px solid var(--border);
  margin-bottom: 16px;
  background: rgba(2, 6, 23, 0.7);
  transition: all 0.3s ease;
}

.lesson:hover {
  border-color: var(--primary);
  transform: translateX(6px);
}

.lesson span {
  font-size: 18px;
  color: var(--primary);
  font-weight: bold;
}

.lesson h4 {
  margin: 0 0 6px;
}

.lesson p {
  margin: 0;
  color: var(--text-soft);
  font-size: 14px;
}

.lesson.locked {
  opacity: 0.6;
}