:root {
  --bg: #0b1220;
  --panel: #0f172a;
  --surface: #111827;
  --text: #e5e7eb;
  --muted: #94a3b8;
  --brand: #0ea5e9;
  --brand-600: #0284c7;
  --accent: #22d3ee;
  --ring: 0 0 0 3px rgba(14, 165, 233, 0.35);
  --radius: 14px;
  --radius-sm: 10px;
  --shadow-1: 0 1px 2px rgba(0,0,0,0.2), 0 8px 24px rgba(0,0,0,0.22);
  --shadow-2: 0 2px 8px rgba(0,0,0,0.25), 0 16px 48px rgba(0,0,0,0.28);
  --success: #10b981;
  --warning: #f59e0b;
  --error: #ef4444;
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

html {
  color-scheme: dark;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: radial-gradient(1200px 800px at 20% -10%, #09223b 0%, transparent 60%), radial-gradient(900px 600px at 120% -10%, #0a1d34 0%, transparent 60%), var(--bg);
  line-height: 1.6;
}

img, svg, video {
  display: block;
  max-width: 100%;
}

.container {
  width: min(1120px, 92%);
  margin: 0 auto;
}

.muted { color: var(--muted); }
.sr-only {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0);
  white-space: nowrap; border: 0;
}

.skip-link {
  position: absolute;
  left: 0.75rem; top: -40px;
  background: var(--brand);
  color: white; padding: 0.5rem 0.75rem;
  border-radius: 8px; text-decoration: none;
  transition: top .2s ease;
}
.skip-link:focus { top: 0.75rem; box-shadow: var(--ring); }

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: saturate(120%) blur(8px);
  background: color-mix(in oklab, var(--bg), transparent 30%);
  border-bottom: 1px solid rgba(255,255,255,0.06);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.75rem 0;
}
.brand { display: inline-flex; align-items: center; gap: 0.6rem; color: inherit; text-decoration: none; font-weight: 700; }
.brand-mark {
  display: grid; place-items: center;
  width: 34px; height: 34px; border-radius: 9px;
  background: linear-gradient(135deg, var(--brand), var(--accent));
  color: #001018; font-weight: 800;
}
.brand-text { letter-spacing: 0.2px; }

.site-nav { 
  position: relative; 
  display: flex; 
  align-items: center; 
  gap: 1.5rem;
}
.nav-links {
  display: flex; align-items: center; gap: 1rem;
  list-style: none; margin: 0; padding: 0;
}
.nav-links a { color: var(--text); text-decoration: none; padding: 0.5rem 0.6rem; border-radius: 8px; }
.nav-links a:hover { background: rgba(255,255,255,0.06); }

.nav-toggle { display: none; background: transparent; color: var(--text); border: 1px dashed rgba(255,255,255,0.15); padding: 0.45rem; border-radius: 10px; }
.nav-toggle:focus { box-shadow: var(--ring); outline: none; }

/* Authentication Components */
.auth-buttons {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.user-menu {
  position: relative;
  display: flex;
  align-items: center;
}

.user-avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--brand), var(--accent));
  display: grid;
  place-items: center;
  cursor: pointer;
  transition: transform 0.2s ease;
}

.user-avatar:hover {
  transform: scale(1.05);
}

.user-avatar span {
  color: #001018;
  font-weight: 700;
  font-size: 0.9rem;
}

.user-dropdown {
  position: absolute;
  top: calc(100% + 0.5rem);
  right: 0;
  min-width: 200px;
  background: color-mix(in oklab, var(--panel), black 6%);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 12px;
  padding: 0.75rem;
  box-shadow: var(--shadow-2);
  transform: scale(0.95) translateY(-6px);
  opacity: 0;
  pointer-events: none;
  transition: transform 0.18s ease, opacity 0.18s ease;
  z-index: 100;
}

.user-menu.open .user-dropdown {
  transform: scale(1) translateY(0);
  opacity: 1;
  pointer-events: auto;
}

.user-info {
  padding-bottom: 0.5rem;
}

.user-info span {
  display: block;
}

.user-dropdown hr {
  border: none;
  height: 1px;
  background: rgba(255,255,255,0.08);
  margin: 0.5rem 0;
}

.dropdown-item {
  width: 100%;
  background: transparent;
  border: none;
  color: var(--text);
  padding: 0.5rem 0.75rem;
  border-radius: 8px;
  text-align: left;
  cursor: pointer;
  transition: background 0.2s ease;
}

.dropdown-item:hover {
  background: rgba(255,255,255,0.06);
}

/* Hero */
.hero {
  padding: 3.5rem 0 2rem;
  background: radial-gradient(700px 300px at 20% -20%, color-mix(in oklab, var(--brand), transparent 60%), transparent 60%);
}
.hero-inner { display: grid; align-items: center; gap: 2rem; grid-template-columns: 1.2fr 0.8fr; }
.hero-copy h1 { font-size: clamp(1.75rem, 3.5vw, 2.5rem); line-height: 1.15; margin: 0 0 0.5rem; }
.hero-copy p { margin: 0 0 1rem; color: var(--muted); max-width: 60ch; }

.search-bar {
  display: grid; grid-template-columns: 1fr repeat(4, minmax(0, max-content)); gap: 0.5rem; align-items: center;
  background: color-mix(in oklab, var(--panel), black 10%);
  padding: 0.75rem; border-radius: var(--radius);
  box-shadow: var(--shadow-1);
}
.search-bar input, .search-bar select { 
  appearance: none; border: 1px solid rgba(255,255,255,0.08);
  background: var(--surface); color: var(--text);
  padding: 0.65rem 0.75rem; border-radius: 10px; 
}
.search-bar input::placeholder { color: #9aa5b1; }
.btn-secondary {
  appearance: none; border: 1px solid rgba(255,255,255,0.12);
  background: transparent; color: var(--text);
  padding: 0.6rem 0.8rem; border-radius: 10px; cursor: pointer;
}
.btn-secondary:hover { background: rgba(255,255,255,0.06); }
.btn-primary {
  display: inline-block; text-decoration: none; text-align: center;
  background: linear-gradient(135deg, var(--brand), var(--brand-600));
  color: white; padding: 0.7rem 1rem; border-radius: 10px; box-shadow: var(--shadow-1);
  border: none; cursor: pointer;
}
.btn-primary:hover { filter: brightness(1.1); }

.btn-large {
  padding: 0.9rem 1.5rem;
  font-size: 1.1rem;
  font-weight: 600;
}

.btn-full {
  width: 100%;
}

/* Results */
.results-bar { padding: 0.75rem 0; }
.results-inner { display: flex; justify-content: space-between; align-items: center; }

/* Courses */
.courses { padding: 0.75rem 0 3.5rem; }
.courses-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(1, minmax(0, 1fr));
}

.card {
  background: color-mix(in oklab, var(--panel), black 8%);
  border: 1px solid rgba(255,255,255,0.06);
  border-radius: var(--radius);
  overflow: hidden; box-shadow: var(--shadow-1);
  transition: transform .18s ease, box-shadow .18s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: var(--shadow-2); }
.card-media { aspect-ratio: 16/9; background: #0b1828; overflow: hidden; }
.card-media img { width: 100%; height: 100%; object-fit: cover; }
.card-body { padding: 0.9rem; display: grid; gap: 0.5rem; }
.card-title { margin: 0; font-size: 1.05rem; line-height: 1.3; }
.card-meta { display: flex; flex-wrap: wrap; gap: 0.6rem 1rem; color: var(--muted); font-size: 0.9rem; }
.tags { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.tag { font-size: 0.75rem; color: #cbd5e1; background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.08); padding: 0.25rem 0.45rem; border-radius: 999px; }
.card-actions { display: flex; align-items: center; justify-content: space-between; margin-top: 0.25rem; }
.card-actions .view-btn { background: transparent; color: var(--brand); border: none; padding: 0.45rem 0.5rem; border-radius: 10px; cursor: pointer; }
.card-actions .view-btn:hover { background: rgba(14,165,233,0.15); }
.card-actions .view-btn.enrolled { color: var(--success); }
.card-actions .view-btn.enrolled:hover { background: rgba(16,185,129,0.15); }

/* Wishlist badge */
.wishlist-badge {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  background: rgba(239, 68, 68, 0.9);
  color: white;
  padding: 0.25rem 0.5rem;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 600;
  backdrop-filter: blur(4px);
}

/* Course Details Page */
.course-details-page {
  padding-top: 0;
}

.course-hero {
  padding: 2rem 0;
  background: radial-gradient(600px 400px at 50% -20%, color-mix(in oklab, var(--brand), transparent 70%), transparent 60%);
}

.course-hero-inner {
  display: grid;
  gap: 2rem;
}

.back-button {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: transparent;
  border: 1px solid rgba(255,255,255,0.12);
  color: var(--text);
  padding: 0.5rem 1rem;
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.2s ease;
  width: fit-content;
  margin-bottom: 1rem;
}

.back-button:hover {
  background: rgba(255,255,255,0.06);
}

.course-header {
  display: grid;
  grid-template-columns: 1fr 400px;
  gap: 3rem;
  align-items: start;
}

.course-info h1 {
  font-size: clamp(1.5rem, 3vw, 2.25rem);
  line-height: 1.2;
  margin: 0 0 1rem;
}

.course-description {
  font-size: 1.1rem;
  color: var(--muted);
  margin: 0 0 1.5rem;
  max-width: 60ch;
}

.course-meta {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.meta-item {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.meta-label {
  font-size: 0.9rem;
  color: var(--muted);
  font-weight: 500;
}

.course-rating {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.rating-stars {
  font-size: 1.2rem;
}

.course-media {
  display: grid;
  gap: 1.5rem;
}

.course-media img {
  width: 100%;
  border-radius: var(--radius);
  border: 1px solid rgba(255,255,255,0.06);
  aspect-ratio: 16/9;
  object-fit: cover;
}

.course-actions {
  display: grid;
  gap: 0.75rem;
}

.course-content {
  padding: 3rem 0;
}

.content-tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 2rem;
  border-bottom: 1px solid rgba(255,255,255,0.08);
}

.tab-btn {
  background: transparent;
  border: none;
  color: var(--muted);
  padding: 1rem 1.5rem;
  border-radius: 10px 10px 0 0;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
}

.tab-btn.active {
  color: var(--text);
  background: rgba(255,255,255,0.04);
}

.tab-btn.active::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--brand);
}

.tab-btn:hover:not(.active) {
  color: var(--text);
  background: rgba(255,255,255,0.02);
}

.tab-content {
  min-height: 400px;
}

.tab-pane {
  display: none;
}

.tab-pane.active {
  display: block;
}

.tab-pane h3 {
  margin: 0 0 1rem;
  color: var(--text);
}

.learning-objectives,
.requirements {
  list-style: none;
  padding: 0;
  display: grid;
  gap: 0.75rem;
}

.learning-objectives li,
.requirements li {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  padding: 0.75rem;
  background: rgba(255,255,255,0.02);
  border-radius: 10px;
  border: 1px solid rgba(255,255,255,0.06);
}

.learning-objectives li::before {
  content: '✓';
  color: var(--success);
  font-weight: bold;
  flex-shrink: 0;
}

.requirements li::before {
  content: '•';
  color: var(--brand);
  font-weight: bold;
  flex-shrink: 0;
}

.curriculum-section {
  margin-bottom: 2rem;
}

.curriculum-section h4 {
  margin: 0 0 1rem;
  padding: 1rem;
  background: rgba(255,255,255,0.04);
  border-radius: 10px;
  border: 1px solid rgba(255,255,255,0.08);
}

.lesson-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.lesson-item:last-child {
  border-bottom: none;
}

.lesson-duration {
  color: var(--muted);
  font-size: 0.9rem;
}

.reviews-summary {
  margin-bottom: 2rem;
}

.overall-rating {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.5rem;
  background: rgba(255,255,255,0.02);
  border-radius: var(--radius);
  border: 1px solid rgba(255,255,255,0.06);
}

.rating-number {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text);
}

.rating-count {
  color: var(--muted);
}

.review-item {
  padding: 1.5rem;
  background: rgba(255,255,255,0.02);
  border-radius: var(--radius);
  border: 1px solid rgba(255,255,255,0.06);
  margin-bottom: 1rem;
}

.review-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
}

.reviewer-name {
  font-weight: 600;
}

.review-text {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

/* Modal */
.modal[hidden] { display: none; }
.modal { position: fixed; inset: 0; z-index: 100; }
.modal-backdrop { position: absolute; inset: 0; background: rgba(6, 9, 16, 0.7); backdrop-filter: blur(2px); }
.modal-dialog {
  position: relative; z-index: 101; margin: 5vh auto 0; width: min(900px, 92%);
  background: color-mix(in oklab, var(--panel), black 6%);
  border: 1px solid rgba(255,255,255,0.08); border-radius: var(--radius);
  box-shadow: var(--shadow-2);
}
.modal-close { position: absolute; top: 10px; right: 10px; background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.08); color: var(--text); border-radius: 10px; padding: 0.4rem 0.5rem; cursor: pointer; }
.modal-close:hover { background: rgba(255,255,255,0.12); }
.modal-body { display: grid; grid-template-columns: 1fr 1.2fr; gap: 1rem; padding: 1rem; }
.modal-body img { width: 100%; border-radius: var(--radius-sm); border: 1px solid rgba(255,255,255,0.06); }
.modal-content h2 { margin: 0 0 0.25rem; }
.modal-meta { display: flex; flex-wrap: wrap; gap: 0.5rem 1rem; color: var(--muted); margin: 0.25rem 0 0.5rem; }

.modal-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 1rem;
}

/* Authentication Modals */
.auth-modal .modal-dialog {
  max-width: 400px;
  margin: 10vh auto 0;
}

.auth-body {
  display: block;
  padding: 2rem;
}

.auth-header {
  text-align: center;
  margin-bottom: 2rem;
}

.auth-header h2 {
  margin: 0 0 0.5rem;
  font-size: 1.5rem;
}

.auth-header p {
  margin: 0;
  color: var(--muted);
}

.auth-form {
  display: grid;
  gap: 1.25rem;
}

.form-group {
  display: grid;
  gap: 0.5rem;
}

.form-group label {
  font-weight: 500;
  color: var(--text);
}

.form-group input {
  appearance: none;
  border: 1px solid rgba(255,255,255,0.12);
  background: var(--surface);
  color: var(--text);
  padding: 0.75rem 1rem;
  border-radius: 10px;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.form-group input:focus {
  outline: none;
  border-color: var(--brand);
  box-shadow: var(--ring);
}

.form-group input::placeholder {
  color: var(--muted);
}

.auth-footer {
  text-align: center;
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(255,255,255,0.08);
}

.auth-footer p {
  margin: 0;
  color: var(--muted);
}

.link-btn {
  background: transparent;
  border: none;
  color: var(--brand);
  cursor: pointer;
  text-decoration: underline;
  font-size: inherit;
}

.link-btn:hover {
  color: var(--accent);
}

/* Footer */
.site-footer { border-top: 1px solid rgba(255,255,255,0.06); padding: 1.25rem 0 3rem; }
.footer-inner { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.footer-links { display: flex; gap: 1rem; }
.footer-links a { color: var(--muted); text-decoration: none; }
.footer-links a:hover { color: var(--text); }

/* Media queries */
@media (max-width: 900px) {
  .hero-inner { grid-template-columns: 1fr; }
  .modal-body { grid-template-columns: 1fr; }
  .course-header { grid-template-columns: 1fr; gap: 2rem; }
  .course-media { order: -1; }
}

@media (max-width: 768px) {
  .nav-toggle { display: inline-grid; place-items: center; }
  .site-nav { position: absolute; right: 0; top: 100%; width: min(320px, 92vw); }
  .nav-links {
    position: absolute; right: 0; top: 0.5rem;
    flex-direction: column; align-items: stretch; gap: 0.25rem;
    background: color-mix(in oklab, var(--panel), black 6%);
    border: 1px solid rgba(255,255,255,0.08);
    border-radius: 12px; padding: 0.5rem; box-shadow: var(--shadow-2);
    transform-origin: top right; transform: scale(0.98) translateY(-6px);
    opacity: 0; pointer-events: none; transition: transform .18s ease, opacity .18s ease;
  }
  .site-nav.open .nav-links { transform: scale(1) translateY(0); opacity: 1; pointer-events: auto; }
  .auth-buttons { 
    position: absolute; 
    top: 0.5rem; 
    right: 0;
    background: color-mix(in oklab, var(--panel), black 6%);
    border: 1px solid rgba(255,255,255,0.08);
    border-radius: 12px; 
    padding: 0.75rem; 
    box-shadow: var(--shadow-2);
    transform-origin: top right; 
    transform: scale(0.98) translateY(-6px);
    opacity: 0; 
    pointer-events: none; 
    transition: transform .18s ease, opacity .18s ease;
    flex-direction: column;
  }
  .site-nav.open .auth-buttons { 
    transform: scale(1) translateY(0); 
    opacity: 1; 
    pointer-events: auto; 
  }
  .search-bar { grid-template-columns: 1fr; }
  .course-meta { grid-template-columns: 1fr; }
  .content-tabs { flex-wrap: wrap; }
}

@media (min-width: 600px) {
  .courses-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (min-width: 900px) {
  .courses-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}
@media (min-width: 1200px) {
  .courses-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* Decorative */
.hero-media { display: grid; place-items: center; }
.hero-art {
  width: clamp(260px, 40vw, 420px); height: clamp(220px, 32vw, 340px);
  border-radius: 24px;
  background:
    radial-gradient(120px 80px at 75% 75%, rgba(34, 211, 238, 0.6), transparent 60%),
    radial-gradient(140px 100px at 35% 35%, rgba(14, 165, 233, 0.7), transparent 60%),
    linear-gradient(180deg, rgba(255,255,255,0.08), rgba(255,255,255,0));
  border: 1px solid rgba(255,255,255,0.08);
  box-shadow: 0 40px 120px rgba(14,165,233,0.15), inset 0 0 60px rgba(255,255,255,0.06);
}

/* Utility classes */
.hidden { display: none !important; }
.text-center { text-align: center; }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-error { color: var(--error); }