/* ---------- Tokens ---------- */
:root {
  --bg: #faf6f0;
  --surface: #ffffff;
  --surface-2: #f4eee6;
  --text: #2b2723;
  --muted: #6f6861;
  --border: #e6ded3;
  --accent: #c8452c;
  --accent-soft: #fbe9e4;
  --green: #2e8b57;
  --green-soft: #e3f4ea;
  --amber: #b86e00;
  --amber-soft: #fff3dc;
  --blue: #2f6fb3;
  --blue-soft: #e4eefb;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 6px 20px rgba(60,40,20,.06);
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #17140f;
    --surface: #211d18;
    --surface-2: #2a251f;
    --text: #f1ebe3;
    --muted: #a59c91;
    --border: #35302a;
    --accent: #ff7b5c;
    --accent-soft: #3a221b;
    --green: #5ccf8a;
    --green-soft: #1d3527;
    --amber: #ffb347;
    --amber-soft: #3b2d12;
    --blue: #7fb3ff;
    --blue-soft: #1e2d44;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 6px 20px rgba(0,0,0,.25);
  }
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }
html { color-scheme: light dark; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.5;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); }
h1, h2, h3 { line-height: 1.2; margin: 0 0 .5rem; }
h1 { font-size: 1.85rem; }
h2 { font-size: 1.3rem; }
h3 { font-size: 1.05rem; }
p { margin: 0 0 .75rem; }
.muted { color: var(--muted); }
.small { font-size: .875rem; }
.center { text-align: center; }
.mt { margin-top: 1rem; }
.mb { margin-bottom: 1rem; }
.row { display: flex; flex-wrap: wrap; gap: .75rem; align-items: center; }
.row.between { justify-content: space-between; }
.stack { display: flex; flex-direction: column; gap: 1rem; }
.hidden { display: none !important; }

.container {
  max-width: 940px;
  margin: 0 auto;
  padding: 1.5rem 1rem 5rem;
}

/* ---------- Header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  padding: .6rem 1rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem 1.25rem;
}
.brand {
  font-weight: 800;
  text-decoration: none;
  color: var(--text);
  display: inline-flex;
  align-items: center;
  gap: .45rem;
  font-size: 1.05rem;
  white-space: nowrap;
}
.brand-icon { font-size: 1.3rem; }
.nav { display: flex; flex-wrap: wrap; gap: .2rem; }
.nav-link {
  text-decoration: none;
  color: var(--muted);
  padding: .35rem .7rem;
  border-radius: 999px;
  font-size: .92rem;
  font-weight: 500;
  white-space: nowrap;
}
.nav-link:hover { background: var(--surface-2); color: var(--text); }
.nav-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 700; }

/* ---------- Cards & layout ---------- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow);
}
.card + .card { margin-top: 1rem; }
.card h2 { margin-bottom: .75rem; }
.grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}
.grid .card + .card { margin-top: 0; }
.section-title {
  display: flex;
  align-items: baseline;
  gap: .6rem;
  flex-wrap: wrap;
  margin-bottom: .25rem;
}
.section-title .en { color: var(--muted); font-weight: 500; font-size: 1rem; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .4rem;
  padding: .6rem 1.1rem;
  border-radius: 10px;
  font: inherit;
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  text-decoration: none;
  transition: transform .05s ease, background .15s ease;
}
.btn:hover { background: var(--surface-2); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: color-mix(in srgb, var(--accent) 88%, black); }
.btn-ghost { background: transparent; border-color: transparent; color: var(--muted); }
.btn-ghost:hover { background: var(--surface-2); color: var(--text); }
.btn-lg { font-size: 1.1rem; padding: .85rem 1.5rem; }
.btn-sm { font-size: .85rem; padding: .35rem .7rem; }
.btn-block { width: 100%; }
.icon-btn {
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 999px;
  width: 2.5rem;
  height: 2.5rem;
  font-size: 1.2rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.icon-btn:hover { background: var(--surface-2); }

/* ---------- Chips, badges, stats ---------- */
.chip {
  display: inline-flex;
  align-items: center;
  gap: .3rem;
  padding: .15rem .6rem;
  border-radius: 999px;
  font-size: .8rem;
  font-weight: 600;
  background: var(--surface-2);
  color: var(--muted);
}
.chip.accent { background: var(--accent-soft); color: var(--accent); }
.chip.green { background: var(--green-soft); color: var(--green); }
.chip.amber { background: var(--amber-soft); color: var(--amber); }
.chip.blue { background: var(--blue-soft); color: var(--blue); }
.stats { display: flex; flex-wrap: wrap; gap: 1rem 2rem; }
.stat .num { font-size: 2rem; font-weight: 800; line-height: 1.1; }
.stat .label { color: var(--muted); font-size: .85rem; }
.progress { height: 6px; background: var(--border); border-radius: 999px; overflow: hidden; }
.progress i { display: block; height: 100%; background: var(--accent); transition: width .2s ease; }

/* ---------- Forms ---------- */
label { font-weight: 600; font-size: .9rem; }
select, input[type="text"], input[type="number"] {
  font: inherit;
  padding: .45rem .6rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
}
.check { display: flex; align-items: flex-start; gap: .6rem; cursor: pointer; font-weight: 500; }
.check input { margin-top: .3rem; width: 1.1rem; height: 1.1rem; accent-color: var(--accent); }

/* ---------- Flashcards ---------- */
.session-top { display: flex; align-items: center; gap: .75rem; margin-bottom: .75rem; }
.session-top .progress { flex: 1; }
.flashcard {
  min-height: 240px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: .6rem;
  padding: 2rem 1.25rem;
}
.flashcard .lang-tag {
  font-size: .75rem;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
  font-weight: 700;
}
.flashcard .word { font-size: 2.1rem; font-weight: 800; line-height: 1.15; }
.flashcard .word.small-word { font-size: 1.5rem; }
.flashcard .note { color: var(--muted); font-size: .9rem; }
.flashcard .example { color: var(--muted); font-style: italic; margin-top: .25rem; }
.flashcard .divider { width: 60px; height: 2px; background: var(--border); margin: .5rem 0; }
.answer-form { width: 100%; max-width: 480px; display: flex; flex-direction: column; gap: .6rem; }
.answer-input {
  font: inherit;
  font-size: 1.25rem;
  padding: .7rem 1rem;
  width: 100%;
  border: 2px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  color: var(--text);
  text-align: center;
}
.answer-input:focus { outline: none; border-color: var(--accent); }
.accent-keys { display: flex; flex-wrap: wrap; justify-content: center; gap: .35rem; }
.accent-keys button {
  min-width: 2.4rem;
  padding: .35rem .5rem;
  font: inherit;
  font-size: 1.1rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
}
.accent-keys button:hover { background: var(--surface-2); }
.result {
  width: 100%;
  max-width: 480px;
  padding: .75rem 1rem;
  border-radius: 10px;
  border-left: 4px solid var(--border);
  background: var(--surface-2);
  text-align: left;
}
.result.correct { border-color: var(--green); background: var(--green-soft); }
.result.almost { border-color: var(--amber); background: var(--amber-soft); }
.result.wrong { border-color: var(--accent); background: var(--accent-soft); }
.result .headline { font-weight: 700; }
.result .answer { font-size: 1.3rem; font-weight: 800; margin: .15rem 0; }
.rating-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: .5rem;
  width: 100%;
  max-width: 520px;
  margin-top: .5rem;
}
.rating-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: .1rem;
  padding: .6rem .3rem;
  border-radius: 10px;
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}
.rating-btn small { font-weight: 500; color: var(--muted); font-size: .75rem; }
.rating-btn .key { font-size: .7rem; color: var(--muted); font-weight: 500; }
.rating-btn.again { border-color: var(--accent); }
.rating-btn.hard { border-color: var(--amber); }
.rating-btn.good { border-color: var(--green); }
.rating-btn.easy { border-color: var(--blue); }
.rating-btn.is-default { box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 30%, transparent); }
.rating-btn:hover { background: var(--surface-2); }
.actions { display: flex; flex-wrap: wrap; gap: .5rem; justify-content: center; margin-top: .25rem; }
.kbd-hint { color: var(--muted); font-size: .8rem; }
kbd {
  font-family: inherit;
  font-size: .75rem;
  padding: .05rem .35rem;
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 5px;
  background: var(--surface-2);
}
.deck-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem .75rem;
  padding: .6rem 0;
  border-top: 1px solid var(--border);
}
.deck-row:first-of-type { border-top: 0; }
.deck-row .title { font-weight: 600; flex: 1; min-width: 160px; }
.mode-card { display: flex; flex-direction: column; gap: .6rem; }
.mode-card .big { font-size: 1.6rem; font-weight: 800; }

/* ---------- Class resources ---------- */
.unit { scroll-margin-top: 80px; }
.unit-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: .5rem 1rem; margin-bottom: .5rem; }
.resource { display: flex; flex-direction: column; gap: .5rem; }
.resource-head { display: flex; gap: .7rem; align-items: flex-start; }
.resource-icon { font-size: 1.5rem; line-height: 1; flex-shrink: 0; }
.resource-title { font-weight: 700; }
.resource-meta { color: var(--muted); font-size: .85rem; display: flex; flex-wrap: wrap; gap: .4rem .75rem; }
.resource-actions { display: flex; flex-wrap: wrap; gap: .4rem; margin-top: auto; }
.badge-due { color: var(--amber); font-weight: 600; }
.badge-overdue { color: var(--accent); font-weight: 600; }
.viewer { grid-column: 1 / -1; }
.pdf-frame { width: 100%; height: 72vh; border: 1px solid var(--border); border-radius: 10px; background: #fff; }
.video-frame { width: 100%; aspect-ratio: 16 / 9; border: 0; border-radius: 10px; background: #000; }
.embed-frame { width: 100%; height: 500px; border: 0; border-radius: 10px; }

/* ---------- Readings & grammar ---------- */
.reading p { line-height: 1.7; }
.reading ol { margin: 0; padding-left: 1.25rem; }
.reading li { margin-bottom: .35rem; }
.examples { width: 100%; border-collapse: collapse; margin-top: .5rem; }
.examples td { padding: .35rem .6rem .35rem 0; border-top: 1px solid var(--border); vertical-align: top; }
.examples td:first-child { font-weight: 600; }

/* ---------- Home ---------- */
.hero { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: .75rem; margin-bottom: 1.25rem; }
.streak { font-size: 1rem; font-weight: 700; padding: .4rem .8rem; }
.due-list { list-style: none; margin: 0; padding: 0; }
.due-list li { display: flex; flex-wrap: wrap; gap: .3rem .75rem; align-items: baseline; padding: .5rem 0; border-top: 1px solid var(--border); }
.due-list li:first-child { border-top: 0; }
.due-list .t { font-weight: 600; flex: 1; min-width: 180px; }
.tip { border-left: 3px solid var(--amber); padding-left: .8rem; color: var(--muted); }

/* ---------- Progress ---------- */
.heatmap { display: grid; grid-template-columns: repeat(14, 1fr); gap: 4px; max-width: 420px; }
.heatmap i { display: block; aspect-ratio: 1; border-radius: 3px; background: var(--border); }
.heatmap i.on { background: var(--green); }
.heatmap i.today { outline: 2px solid var(--accent); outline-offset: 1px; }
.weak-list { list-style: none; margin: 0; padding: 0; }
.weak-list li { display: flex; justify-content: space-between; gap: .75rem; padding: .4rem 0; border-top: 1px solid var(--border); }
.weak-list li:first-child { border-top: 0; }

/* ---------- Misc ---------- */
.empty { color: var(--muted); text-align: center; padding: 2rem 1rem; }
.error { color: var(--accent); font-weight: 600; }
.toast {
  position: fixed;
  left: 50%;
  bottom: 1.5rem;
  transform: translateX(-50%);
  background: var(--text);
  color: var(--bg);
  padding: .6rem 1rem;
  border-radius: 999px;
  font-weight: 600;
  box-shadow: var(--shadow);
  z-index: 50;
  animation: toast-in .2s ease;
}
@keyframes toast-in { from { opacity: 0; transform: translate(-50%, 8px); } to { opacity: 1; transform: translate(-50%, 0); } }
.soon { text-align: center; padding: 3rem 1rem; }
.soon .big-icon { font-size: 3rem; }

@media (max-width: 600px) {
  .container { padding: 1rem .9rem 4rem; }
  h1 { font-size: 1.5rem; }
  .flashcard { padding: 1.5rem .9rem; min-height: 200px; }
  .flashcard .word { font-size: 1.7rem; }
  .pdf-frame { height: 60vh; }
  .nav-link { font-size: .85rem; padding: .3rem .55rem; }
}