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

:root {
  --bg: #0a0a0a;
  --surface: #1a1a1a;
  --surface-alt: #222;
  --border: #333;
  --text: #f0f0f0;
  --text-muted: #999;
  --accent: #4a90d9;
  --accent-dark: #357abd;
  --green: #4caf50;
  --green-dim: rgba(76,175,80,0.15);
  --pink: #ff4757;
  --orange: #ff6b35;
  --yellow: #ffd32a;
  --shadow: 0 4px 20px rgba(0,0,0,0.4);
  --radius: 12px;
  --radius-sm: 8px;
  --safe-top: env(safe-area-inset-top, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
  --safe-left: env(safe-area-inset-left, 0px);
  --safe-right: env(safe-area-inset-right, 0px);
}

html {
  background: var(--bg);
  -webkit-text-size-adjust: 100%;
  -ms-text-size-adjust: 100%;
}

body {
  color: var(--text);
  background: var(--bg);
  font-family: 'Roboto', 'Segoe UI', Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  user-select: none;
  overscroll-behavior-y: contain;
  padding-top: var(--safe-top);
  padding-left: var(--safe-left);
  padding-right: var(--safe-right);
}

a { color: var(--accent); text-decoration: none; -webkit-tap-highlight-color: transparent; }
a:hover { text-decoration: underline; color: var(--accent-dark); }

button { -webkit-tap-highlight-color: transparent; touch-action: manipulation; }

[hidden] { display: none !important; }

/* ── HEADER ──────────────────────────────── */

.feed-shell {
  width: 100%;
  max-width: 480px;
  margin: 0 auto;
  min-height: 100vh;
  min-height: 100dvh;
}

.feed-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(135deg, #1a1a2e, #16213e);
  box-shadow: 0 2px 20px rgba(0,0,0,0.5);
  border-bottom: 1px solid rgba(74,144,217,0.2);
  padding-top: var(--safe-top);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 12px 6px;
}

.wordmark {
  color: #fff;
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.5px;
  text-decoration: none;
}
.wordmark span { color: var(--accent); }

.header-stats {
  display: flex;
  gap: 4px;
}

.stat-pill {
  display: flex;
  align-items: center;
  gap: 3px;
  padding: 4px 8px;
  border-radius: 16px;
  background: rgba(255,255,255,0.08);
  font-size: 11px;
  font-weight: 600;
  color: #fff;
  border: 1px solid rgba(255,255,255,0.1);
  white-space: nowrap;
}
.stat-icon { font-size: 12px; }

#stat-xp .stat-icon { color: var(--yellow); }
#stat-streak .stat-icon { color: var(--orange); }
#stat-combo .stat-icon { color: #ff4757; }
#stat-level .stat-icon { color: var(--accent); }

.tagline-bar {
  text-align: center;
  padding: 2px 0 8px;
  color: rgba(255,255,255,0.5);
  font-size: 10px;
  letter-spacing: 1px;
  text-transform: uppercase;
}

/* ── FEED ───────────────────────────────── */

.feed {
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0;
}

.feed-sentinel {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 40px 0;
  padding-bottom: calc(40px + var(--safe-bottom));
  color: var(--text-muted);
  font-size: 12px;
}

.sentinel-ring {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  border: 2px solid var(--border);
  border-top-color: var(--accent);
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── TIKTOK CARD ────────────────────────── */

.tiktok-card {
  background: var(--surface);
  border-radius: 0;
  margin: 0;
  box-shadow: none;
  overflow: hidden;
  border: none;
  border-bottom: 1px solid var(--border);
  position: relative;
  min-height: 70vh;
  min-height: 70dvh;
  display: flex;
  flex-direction: column;
}

.card-content-scroll {
  flex: 1;
  padding: 16px 16px 8px;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain;
  scrollbar-width: none;
}
.card-content-scroll::-webkit-scrollbar { display: none; }

.card-footer {
  padding: 10px 16px;
  padding-bottom: calc(10px + var(--safe-bottom));
  border-top: 1px solid var(--border);
  background: rgba(255,255,255,0.02);
  text-align: center;
  flex-shrink: 0;
}

.swipe-hint {
  color: var(--text-muted);
  font-size: 11px;
  letter-spacing: 0.5px;
  animation: pulse 2s ease-in-out infinite;
}

.swipe-arrow {
  display: inline-block;
  animation: bounce 1.5s ease-in-out infinite;
  margin-right: 4px;
}

@keyframes pulse { 0%, 100% { opacity: 0.4; } 50% { opacity: 0.8; } }
@keyframes bounce { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-4px); } }

/* ── CARD TOP ROW ───────────────────────── */

.card-top-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
  gap: 8px;
}

.card-tag {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 16px;
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.8px;
  text-transform: uppercase;
  color: #fff;
  flex-shrink: 0;
}
.tag-dictionary { background: var(--accent); }
.tag-science { background: var(--green); }
.tag-math { background: var(--orange); }

.card-category {
  display: inline-block;
  padding: 3px 8px;
  border-radius: 10px;
  font-size: 9px;
  font-weight: 600;
  color: #fff;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

/* ── CARD CONTENT ───────────────────────── */

.card-word-row {
  margin-bottom: 6px;
}

.card-word {
  font-size: 26px;
  font-weight: 700;
  color: #fff;
  line-height: 1.2;
  word-break: break-word;
}

.card-word-science { font-size: 20px; }
.card-word-math { font-size: 20px; }

.card-pron {
  color: var(--text-muted);
  font-size: 14px;
  font-style: italic;
  margin-bottom: 2px;
}

.card-pos {
  margin-bottom: 10px;
  color: var(--text-muted);
  font-size: 11px;
  font-style: italic;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.card-defs {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 10px;
}

.card-def {
  display: grid;
  grid-template-columns: 20px 1fr;
  gap: 6px;
  font-size: 15px;
  line-height: 1.5;
  color: #ccc;
}

.card-def-num { color: var(--accent); font-weight: 600; }

.card-example {
  padding: 10px 14px;
  margin-bottom: 10px;
  border-left: 3px solid var(--accent);
  background: rgba(74,144,217,0.08);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: 14px;
  color: #bbb;
  font-style: italic;
}

.example-label {
  display: inline-block;
  margin-right: 4px;
  padding: 2px 6px;
  border-radius: 8px;
  background: rgba(74,144,217,0.2);
  color: var(--accent);
  font-size: 9px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-style: normal;
}

.card-actions {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding-top: 10px;
  border-top: 1px solid var(--border);
  margin-top: 6px;
}

.detail-link {
  font-size: 13px;
  color: var(--accent);
  font-weight: 500;
  padding: 10px 16px;
  border-radius: 20px;
  border: 1px solid rgba(74,144,217,0.3);
  transition: all 0.2s;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
}
.detail-link:hover {
  background: rgba(74,144,217,0.1);
  text-decoration: none;
}

/* ── LESSON CONTENT (science) ───────────── */

.lesson-content {
  margin: 10px 0;
  padding: 14px;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  color: #bbb;
  line-height: 1.8;
  word-break: break-word;
}

.key-facts {
  margin-bottom: 10px;
  padding: 12px 14px;
  background: rgba(76,175,80,0.08);
  border: 1px solid rgba(76,175,80,0.2);
  border-radius: var(--radius-sm);
  font-size: 13px;
}
.key-facts strong {
  color: var(--green);
  display: block;
  margin-bottom: 6px;
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 1px;
}
.key-facts ul { margin: 0; padding-left: 16px; }
.key-facts li { margin-bottom: 4px; color: #aaa; }
.key-facts li:last-child { margin-bottom: 0; }

/* ── LEVEL BADGES ───────────────────────── */

.level-badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.level-beginner { background: rgba(76,175,80,0.2); color: #66bb6a; border: 1px solid rgba(76,175,80,0.3); }
.level-intermediate { background: rgba(74,144,217,0.2); color: #64b5f6; border: 1px solid rgba(74,144,217,0.3); }
.level-advanced { background: rgba(255,71,87,0.2); color: #ff6b7a; border: 1px solid rgba(255,71,87,0.3); }

/* ── QUIZ ───────────────────────────────── */

.quiz-section { margin-top: 14px; }
.quiz-title {
  color: #fff;
  font-size: 16px;
  margin-bottom: 10px;
  font-weight: 600;
}

.quiz-q { margin-bottom: 14px; }

.quiz-question {
  color: #ddd;
  font-size: 15px;
  font-weight: 500;
  margin-bottom: 8px;
  line-height: 1.5;
  word-break: break-word;
}

.quiz-opts {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.quiz-opt {
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-alt);
  color: #ddd;
  font-size: 15px;
  cursor: pointer;
  transition: all 0.15s;
  text-align: left;
  min-height: 52px;
  display: flex;
  align-items: center;
  word-break: break-word;
}
.quiz-opt:active:not(:disabled) {
  transform: scale(0.97);
}
.quiz-opt:hover:not(:disabled) {
  border-color: var(--accent);
  color: #fff;
  background: rgba(74,144,217,0.1);
}
.quiz-opt.correct {
  border-color: var(--green);
  background: rgba(76,175,80,0.15);
  color: #66bb6a;
}
.quiz-opt.wrong {
  border-color: var(--pink);
  background: rgba(255,71,87,0.1);
  color: #ff6b7a;
}
.quiz-opt:disabled { cursor: default; opacity: 0.8; }

.quiz-feedback {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 6px;
  line-height: 1.6;
  padding: 10px 12px;
  background: rgba(255,255,255,0.03);
  border-radius: var(--radius-sm);
  word-break: break-word;
}
.quiz-correct { color: #66bb6a; font-weight: 600; }
.quiz-wrong { color: #ff6b7a; font-weight: 600; }

/* ── MATH CARDS ─────────────────────────── */

.math-question {
  margin: 14px 0;
  padding: 18px 16px;
  background: linear-gradient(135deg, rgba(255,107,53,0.1), rgba(255,211,42,0.05));
  border: 1px solid rgba(255,107,53,0.2);
  border-radius: var(--radius);
  font-size: 20px;
  font-weight: 600;
  color: #fff;
  text-align: center;
  letter-spacing: 0.5px;
  word-break: break-word;
}

.math-opts {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-bottom: 10px;
}

.math-opt {
  padding: 16px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-alt);
  color: #fff;
  font-size: 18px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s;
  min-height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.math-opt:active:not(:disabled) {
  transform: scale(0.95);
}
.math-opt:hover:not(:disabled) {
  border-color: var(--orange);
  background: rgba(255,107,53,0.1);
}
.math-opt.correct {
  border-color: var(--green);
  background: rgba(76,175,80,0.15);
  color: #66bb6a;
}
.math-opt.wrong {
  border-color: var(--pink);
  background: rgba(255,71,87,0.1);
  color: #ff6b7a;
}
.math-opt:disabled { cursor: default; }

.math-feedback {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.6;
  padding: 10px 12px;
  background: rgba(255,255,255,0.03);
  border-radius: var(--radius-sm);
  word-break: break-word;
}

/* ── CONFETTI ───────────────────────────── */

.confetti-particle {
  position: fixed;
  width: 8px;
  height: 8px;
  border-radius: 2px;
  pointer-events: none;
  z-index: 9999;
  animation: confetti-fly 0.8s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
}

@keyframes confetti-fly {
  0% {
    opacity: 1;
    transform: translate(0, 0) rotate(0deg) scale(1);
  }
  100% {
    opacity: 0;
    transform: translate(var(--dx), var(--dy)) rotate(var(--r)) scale(0.3);
  }
}

/* ── FLOATING SCORE ─────────────────────── */

.float-score {
  position: fixed;
  z-index: 10001;
  font-size: 20px;
  font-weight: 700;
  pointer-events: none;
  transform: translateX(-50%);
  animation: float-up 0.9s ease-out forwards;
  text-shadow: 0 2px 8px rgba(0,0,0,0.6);
  white-space: nowrap;
}

@keyframes float-up {
  0% { opacity: 1; transform: translateX(-50%) translateY(0) scale(1); }
  60% { opacity: 1; transform: translateX(-50%) translateY(-50px) scale(1.2); }
  100% { opacity: 0; transform: translateX(-50%) translateY(-90px) scale(0.8); }
}

/* ── LEVEL UP TOAST ─────────────────────── */

.level-up-toast {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.5);
  z-index: 10000;
  opacity: 0;
  transition: all 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
  pointer-events: none;
  width: calc(100% - 48px);
  max-width: 320px;
}
.level-up-toast.show {
  opacity: 1;
  transform: translate(-50%, -50%) scale(1);
}

.level-up-inner {
  background: linear-gradient(135deg, #667eea, #764ba2);
  padding: 24px 32px;
  border-radius: 16px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.5);
  text-align: center;
  border: 2px solid rgba(255,255,255,0.2);
}

.level-up-icon {
  display: block;
  font-size: 40px;
  margin-bottom: 8px;
}

.level-up-text {
  display: block;
  color: #fff;
  font-size: 22px;
  font-weight: 700;
  letter-spacing: 1px;
}

/* ── EMPTY ──────────────────────────────── */

.empty-msg {
  padding: 40px 16px;
  color: var(--text-muted);
  text-align: center;
  font-size: 15px;
}

/* ── MEANING PAGE ───────────────────────── */

.meaning-page {
  max-width: 480px;
  margin: 0 auto;
  padding: 16px 16px 30px;
  padding-top: calc(16px + var(--safe-top));
  padding-bottom: calc(30px + var(--safe-bottom));
  background: var(--bg);
  min-height: 100vh;
  min-height: 100dvh;
}
.meaning-page h1 {
  margin-bottom: 4px;
  color: #fff;
  font-size: 30px;
  font-weight: 700;
  word-break: break-word;
}
.meaning-page .pronunciation {
  color: var(--text-muted);
  font-size: 15px;
  font-style: italic;
}
.meaning-page .part-of-speech {
  margin: 4px 0 16px;
  color: var(--text-muted);
  font-size: 13px;
  font-style: italic;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.meaning-page .definition {
  display: grid;
  grid-template-columns: 22px 1fr;
  gap: 4px;
  margin: 6px 0;
  color: #ccc;
  font-size: 15px;
  line-height: 1.6;
}
.meaning-page .definition-number { color: var(--accent); font-weight: 600; }
.meaning-page .example {
  margin: 10px 0 0 24px;
  padding-left: 10px;
  border-left: 2px solid var(--accent);
  color: var(--text-muted);
  font-size: 14px;
  font-style: italic;
}

/* ── RESPONSIVE ─────────────────────────── */

@media (max-width: 380px) {
  .header-inner { padding: 8px 10px 4px; }
  .wordmark { font-size: 18px; }
  .stat-pill { padding: 3px 6px; font-size: 10px; gap: 2px; }
  .stat-icon { font-size: 11px; }
  .card-content-scroll { padding: 14px 12px 6px; }
  .card-word { font-size: 22px; }
  .card-word-science, .card-word-math { font-size: 18px; }
  .math-question { font-size: 18px; padding: 14px 12px; }
  .math-opt { min-height: 52px; font-size: 16px; }
  .quiz-opt { min-height: 48px; font-size: 14px; padding: 12px 14px; }
}

@media (min-width: 768px) {
  .feed-shell { max-width: 520px; }
  .tiktok-card { border-radius: var(--radius); margin: 8px; border: 1px solid var(--border); }
}

/* ── DARK MODE PULL-TO-REFRESH PREVENT ──── */

html, body {
  overscroll-behavior: none;
}