* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg: #111;
  --surface: #181818;
  --surface2: #1e1e1e;
  --text: #ccc;
  --text-dim: #777;
  --accent: #d4952a;
  --accent-dim: rgba(212, 149, 42, 0.12);
  --border: #232323;
  --red: #b33;
  --green: #4a4;
  --blue: #48f;
  --radius: 10px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
  padding-left: env(safe-area-inset-left);
  padding-right: env(safe-area-inset-right);
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 16px;
}

a { color: inherit; text-decoration: none; }
.hidden { display: none !important; }

/* HEADER */
.main-header {
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(17,17,17,0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  padding-top: env(safe-area-inset-top);
}

.main-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 48px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo h1 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
}

nav { display: flex; gap: 2px; }

.nav-link {
  color: var(--text-dim);
  padding: 8px 12px;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 500;
  min-height: 44px;
  display: flex;
  align-items: center;
  transition: color 0.15s;
}

.nav-link.active { color: var(--accent); }

/* SECTIONS */
.section {
  display: none;
  padding: 20px 0 48px;
  min-height: calc(100vh - 48px);
}

.section.active { display: block; }

/* HERO */
.hero {
  padding: 36px 0 28px;
  text-align: center;
}

.hero h2 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text);
  letter-spacing: -0.3px;
}

.hero p {
  color: var(--text-dim);
  max-width: 380px;
  margin: 0 auto 20px;
  font-size: 0.9rem;
}

.btn {
  display: inline-block;
  padding: 12px 24px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.875rem;
  border: none;
  cursor: pointer;
  min-height: 44px;
}

.btn-primary {
  background: var(--accent);
  color: #111;
}

.btn-back {
  background: var(--surface);
  color: var(--text-dim);
  border: 1px solid var(--border);
  margin-bottom: 16px;
  font-size: 0.8rem;
  padding: 10px 14px;
}

.btn-back:active { background: var(--surface2); }

/* FEATURES */
.features {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  padding-bottom: 24px;
}

.feature-card {
  padding: 14px 16px;
  text-align: center;
}

.feature-card h3 {
  font-size: 0.85rem;
  margin-bottom: 2px;
  font-weight: 600;
}

.feature-card p {
  color: var(--text-dim);
  font-size: 0.8rem;
}

/* ============================================
   SEARCH & FILTER
   ============================================ */
.search-bar {
  position: relative;
  margin-top: 10px;
}

.search-icon {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  pointer-events: none;
}

.search-bar input {
  width: 100%;
  padding: 11px 40px 11px 38px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.875rem;
  outline: none;
  min-height: 44px;
  -webkit-appearance: none;
  appearance: none;
}

.search-bar input::placeholder {
  color: var(--text-dim);
}

.search-bar input:focus {
  border-color: #444;
}

.search-clear {
  position: absolute;
  right: 6px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 1.2rem;
  cursor: pointer;
  padding: 8px;
  min-width: 36px;
  min-height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
}

.search-clear:active { background: var(--surface2); }

.filter-row {
  display: flex;
  gap: 6px;
  margin-top: 10px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  padding-bottom: 2px;
}

.filter-btn {
  padding: 6px 12px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-dim);
  font-size: 0.75rem;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  min-height: 34px;
  transition: border-color 0.15s, color 0.15s;
}

.filter-btn:active { background: var(--surface2); }

.filter-btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-dim);
}

.no-results {
  text-align: center;
  color: var(--text-dim);
  padding: 40px 16px;
  font-size: 0.875rem;
}

/* LEARN */
.learn-header {
  margin-bottom: 16px;
}

.learn-header h2 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 0;
}

.module-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 8px;
}

.module-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  cursor: pointer;
  transition: border-color 0.15s;
}

.module-card:hover { border-color: #3a3a3a; }
.module-card:active { background: var(--surface2); }

.module-img {
  margin: -14px -14px 12px -14px;
  border-radius: var(--radius) var(--radius) 0 0;
  overflow: hidden;
  aspect-ratio: 16/9;
  background: #0d0d0d;
}

.module-img img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.module-card h3 {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 2px;
}

.module-card p {
  color: var(--text-dim);
  font-size: 0.78rem;
  margin-bottom: 8px;
  line-height: 1.4;
}

.module-tag {
  display: inline-block;
  padding: 2px 7px;
  border-radius: 4px;
  font-size: 0.65rem;
  font-weight: 600;
  margin-right: 4px;
  background: #1f1f1f;
  color: var(--text-dim);
}

.module-tag.beginner { color: var(--green); }
.module-tag.intermediate { color: var(--blue); }
.module-tag.advanced { color: var(--red); }

/* LESSON */
.lesson-view.hidden { display: none; }

.lesson-hero {
  margin: 0 -16px 16px -16px;
  aspect-ratio: 21/9;
  overflow: hidden;
  background: #0d0d0d;
  border-radius: 0 0 var(--radius) var(--radius);
}

.lesson-hero img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.lesson-title {
  font-size: 1.2rem;
  margin-bottom: 2px;
  font-weight: 600;
}

.lesson-subtitle {
  color: var(--text-dim);
  margin-bottom: 16px;
  font-size: 0.85rem;
}

.lesson-block {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  margin-bottom: 10px;
}

.lesson-block h3 {
  font-size: 0.95rem;
  margin-bottom: 6px;
  font-weight: 600;
}

.lesson-block h4 {
  font-size: 0.85rem;
  margin: 10px 0 4px;
  color: var(--accent);
}

.lesson-block p,
.lesson-block li {
  color: var(--text-dim);
  line-height: 1.6;
  font-size: 0.82rem;
}

.lesson-block ul, .lesson-block ol {
  padding-left: 18px;
  margin: 4px 0;
}

.lesson-block li { margin-bottom: 4px; }

/* DIAGRAM */
.diagram-container {
  background: #0d0d0d;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px;
  margin: 10px -14px;
  text-align: center;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.diagram-container svg {
  display: block;
  margin: 0 auto;
  height: auto;
  min-width: 480px;
  max-width: 100%;
}

.diagram-caption {
  color: var(--text-dim);
  font-size: 0.72rem;
  margin-top: 8px;
  padding: 0 4px;
}

/* TABLE */
.table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 8px -14px;
  padding: 0 14px;
}

.info-table {
  width: 100%;
  border-collapse: collapse;
  margin: 8px 0;
  font-size: 0.78rem;
  min-width: 380px;
}

.info-table th, .info-table td {
  padding: 7px 10px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}

.info-table th {
  color: var(--text);
  font-weight: 600;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.3px;
  position: sticky;
  top: 0;
  background: var(--surface);
}

.info-table td { color: var(--text-dim); }

/* TIP / WARNING */
.tip-box, .warning-box {
  border-left: 3px solid var(--accent);
  padding: 10px 12px;
  margin: 10px 0;
  border-radius: 0 var(--radius) var(--radius) 0;
  background: #161616;
}

.warning-box { border-left-color: var(--red); }

.tip-box .tip-label { font-weight: 600; color: var(--accent); margin-bottom: 2px; font-size: 0.78rem; }
.warning-box .tip-label { font-weight: 600; color: var(--red); margin-bottom: 2px; font-size: 0.78rem; }
.tip-box p, .warning-box p { color: var(--text-dim); font-size: 0.78rem; }

/* STEPS */
.step {
  display: flex;
  gap: 10px;
  margin: 10px 0;
  align-items: flex-start;
}

.step-num {
  background: var(--accent);
  color: #111;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.72rem;
  flex-shrink: 0;
  margin-top: 1px;
}

.step-content h4 { margin: 0 0 2px; color: var(--text); font-size: 0.82rem; }
.step-content p { font-size: 0.78rem; }

/* ABOUT */
.about-content {
  max-width: 480px;
  margin: 0 auto;
}

.about-content h2 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 10px;
}

.about-content p {
  color: var(--text-dim);
  font-size: 0.875rem;
}

.about-stats {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-top: 24px;
}

.stat { text-align: center; }
.stat-num { font-size: 1.4rem; font-weight: 700; color: var(--accent); display: block; }
.stat-label { color: var(--text-dim); font-size: 0.78rem; }

.made-by {
  text-align: center;
  margin-top: 24px;
  font-size: 0.8rem;
  color: var(--text-dim);
  font-style: italic;
}

/* FOOTER */
footer {
  border-top: 1px solid var(--border);
  padding: 14px 0;
  text-align: center;
  color: var(--text-dim);
  font-size: 0.72rem;
}

/* INSTALL BANNER */
.install-banner {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--surface);
  border-top: 1px solid var(--border);
  padding: 12px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  z-index: 200;
  transform: translateY(100%);
  transition: transform 0.3s ease;
  font-size: 0.85rem;
  color: var(--text-dim);
  padding-bottom: calc(12px + env(safe-area-inset-bottom));
}

.install-banner.show { transform: translateY(0); }

.install-btns { display: flex; gap: 8px; flex-shrink: 0; }

.install-btn {
  background: var(--accent);
  color: #111;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  font-weight: 600;
  font-size: 0.8rem;
  cursor: pointer;
  min-height: 36px;
}

.install-dismiss {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 1.2rem;
  cursor: pointer;
  padding: 8px;
  min-width: 36px;
  min-height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ============================================
   DESKTOP
   ============================================ */
@media (min-width: 640px) {
  .container { padding: 0 24px; }
  .main-header .container { height: 52px; }
  .hero { padding: 56px 0 44px; }
  .hero h2 { font-size: 1.8rem; }
  .features { grid-template-columns: repeat(3, 1fr); }
  .module-grid { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .module-card { padding: 18px; }
  .module-img { margin: -18px -18px 14px -18px; }
  .lesson-hero { margin: 0 0 20px 0; border-radius: var(--radius); }
  .lesson-block { padding: 20px; }
  .lesson-title { font-size: 1.4rem; }
  .diagram-container { margin: 12px 0; padding: 16px; }
  .diagram-container svg { min-width: unset; }
  .table-wrap { margin: 10px 0; padding: 0; }
  .info-table th, .info-table td { white-space: normal; }
  .search-bar input { font-size: 0.9rem; }
}

@media (min-width: 900px) {
  .module-grid { grid-template-columns: repeat(3, 1fr); }
}