/* `display: grid/flex` on author CSS overrides the UA rule for [hidden];
   restore it so toggling the `hidden` attribute actually hides elements. */
[hidden] { display: none !important; }

:root {
  --lux-red: #ED2939;
  --lux-blue: #00a1de;
  --accent: #00a1de;
  --accent-2: #5b6cff;
  --bg: #f4f6fb;
  --bg-elev: #ffffff;
  --surface: #ffffff;
  --text: #16202c;
  --text-soft: #5c6b7a;
  --border: #e4e9f1;
  --shadow: 0 10px 30px rgba(20, 40, 80, .08);
  --shadow-lg: 0 24px 60px rgba(20, 40, 80, .16);
  --radius: 18px;
  --radius-sm: 12px;
  --good: #2bb673;
  --hard: #f0a020;
  --again: #ec5b5b;
  --easy: #3ba0ff;
  --maxw: 860px;
}
[data-theme="dark"] {
  --bg: #0e1420;
  --bg-elev: #161e2d;
  --surface: #1b2536;
  --text: #e8eef7;
  --text-soft: #9aa9bd;
  --border: #28344a;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
  --shadow-lg: 0 24px 60px rgba(0,0,0,.5);
  --accent: #2bb6f6;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: radial-gradient(1200px 600px at 80% -10%, rgba(0,161,222,.10), transparent 60%),
              radial-gradient(1000px 500px at -10% 0%, rgba(237,41,57,.07), transparent 55%),
              var(--bg);
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); }
.skip-link { position: absolute; left: -999px; }
.skip-link:focus { left: 12px; top: 12px; background: var(--surface); padding: 8px 14px; border-radius: 8px; z-index: 100; }

/* ---------- Topbar ---------- */
.topbar {
  display: flex; align-items: center; gap: 16px;
  padding: 12px clamp(14px, 4vw, 34px);
  position: sticky; top: 0; z-index: 30;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: saturate(140%) blur(12px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 11px; }
.brand-flag {
  width: 30px; height: 30px; border-radius: 9px; flex: none;
  background: linear-gradient(var(--lux-red) 0 33.3%, #fff 33.3% 66.6%, var(--lux-blue) 66.6% 100%);
  box-shadow: var(--shadow); border: 1px solid rgba(0,0,0,.06);
}
.brand-text { display: flex; flex-direction: column; line-height: 1.05; }
.brand-text strong { font-size: 1.12rem; letter-spacing: -.02em; }
.brand-sub { font-size: .72rem; color: var(--text-soft); }
.tabs { display: flex; gap: 4px; margin: 0 auto; background: var(--bg-elev); padding: 4px; border-radius: 999px; border: 1px solid var(--border); }
.tab {
  border: 0; background: transparent; color: var(--text-soft);
  padding: 8px 16px; border-radius: 999px; cursor: pointer; font-size: .9rem; font-weight: 600;
  transition: .18s;
}
.tab:hover { color: var(--text); }
.tab.is-active { background: var(--accent); color: #fff; box-shadow: 0 4px 14px rgba(0,161,222,.4); }
.icon-btn {
  border: 1px solid var(--border); background: var(--bg-elev); color: var(--text);
  width: 42px; height: 42px; border-radius: 12px; cursor: pointer; font-size: 1.1rem;
  display: grid; place-items: center; transition: .18s; flex: none;
}
.icon-btn:hover { transform: translateY(-1px); box-shadow: var(--shadow); }

/* ---------- Views ---------- */
main { max-width: var(--maxw); margin: 0 auto; padding: clamp(16px, 3vw, 30px); }
.view { display: none; animation: fade .25s ease; }
.view.is-active { display: block; }
@keyframes fade { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }

/* ---------- Study toolbar ---------- */
.study-toolbar { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between; margin-bottom: 18px; }
.chipset { display: flex; gap: 8px; flex-wrap: wrap; }
.chip {
  border: 1px solid var(--border); background: var(--bg-elev); color: var(--text-soft);
  padding: 7px 14px; border-radius: 999px; cursor: pointer; font-weight: 700; font-size: .82rem;
  transition: .16s; user-select: none;
}
.chip small { font-weight: 500; opacity: .7; margin-left: 4px; }
.chip.on { color: #fff; border-color: transparent; }
.chip.on[data-level="A1"] { background: #2bb673; }
.chip.on[data-level="A2"] { background: #00a1de; }
.chip.on[data-level="B1"] { background: #5b6cff; }
.chip.on[data-level="B2"] { background: #9b51e0; }
.study-meta { display: flex; align-items: center; gap: 14px; }
.switch { display: inline-flex; align-items: center; gap: 7px; font-size: .82rem; color: var(--text-soft); cursor: pointer; }
.switch input { width: 16px; height: 16px; accent-color: var(--accent); }
.queue-pill { font-size: .8rem; font-weight: 700; color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent); padding: 6px 12px; border-radius: 999px; }

/* ---------- Flashcard ---------- */
.card-stage { perspective: 1600px; margin: 6px 0 20px; }
.flashcard {
  width: 100%; min-height: 340px; cursor: pointer; outline: none;
}
.flashcard-inner {
  position: relative; width: 100%; min-height: 340px;
  transition: transform .55s cubic-bezier(.2,.8,.2,1); transform-style: preserve-3d;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard:focus-visible .flashcard-inner { outline: 3px solid var(--accent); outline-offset: 4px; border-radius: var(--radius); }
.flashcard-face {
  position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow-lg); padding: clamp(22px, 5vw, 40px);
  display: flex; flex-direction: column; align-items: center; justify-content: center; text-align: center;
}
.flashcard-front { background: linear-gradient(180deg, var(--surface), color-mix(in srgb, var(--accent) 5%, var(--surface))); }
.flashcard-back { transform: rotateY(180deg); }
.card-top { position: absolute; top: 16px; left: 18px; right: 18px; display: flex; justify-content: space-between; align-items: center; }
.pos-tag { font-size: .7rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 800; color: var(--text-soft); background: var(--bg-elev); padding: 4px 10px; border-radius: 999px; border: 1px solid var(--border); }
.level-tag { font-size: .72rem; font-weight: 800; color: var(--accent); }
.headword { font-size: clamp(2rem, 7vw, 3.4rem); font-weight: 800; letter-spacing: -.03em; line-height: 1.05; }
.headword-answer { color: var(--accent); }
.subword { color: var(--text-soft); margin-top: 6px; font-size: 1rem; font-weight: 600; }
.example { margin-top: 18px; max-width: 30ch; color: var(--text-soft); font-size: 1.02rem; line-height: 1.5; font-style: italic; }
.example b { color: var(--text); font-style: normal; }
.example-answer { color: var(--text); font-style: normal; }
.flip-hint { position: absolute; bottom: 16px; left: 0; right: 0; font-size: .74rem; color: var(--text-soft); opacity: .8; }
.flip-hint kbd { background: var(--bg-elev); border: 1px solid var(--border); border-radius: 6px; padding: 1px 6px; font-size: .72rem; }
.translations { list-style: none; padding: 0; margin: 8px 0 0; display: flex; flex-direction: column; gap: 6px; }
.translations li { font-size: 1.06rem; }
.translations .lang { display: inline-block; min-width: 26px; font-size: .66rem; font-weight: 800; color: var(--accent); text-transform: uppercase; margin-right: 8px; }
.lod-link { font-size: .76rem; font-weight: 800; text-decoration: none; background: color-mix(in srgb, var(--accent) 14%, transparent); color: var(--accent); padding: 5px 11px; border-radius: 999px; }
.lod-link:hover { background: var(--accent); color: #fff; }

/* ---------- Controls ---------- */
.flip-bar { display: flex; gap: 10px; justify-content: center; }
.btn {
  border: 1px solid var(--border); background: var(--bg-elev); color: var(--text);
  padding: 12px 22px; border-radius: 14px; font-weight: 700; cursor: pointer; font-size: .95rem;
  transition: .16s;
}
.btn:hover { transform: translateY(-1px); box-shadow: var(--shadow); }
.btn.primary { background: var(--accent); color: #fff; border-color: transparent; box-shadow: 0 8px 22px rgba(0,161,222,.35); }
.btn.big { padding: 14px 40px; font-size: 1.02rem; }
.btn.danger { background: var(--again); color: #fff; border-color: transparent; }
.grade-bar { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; }
.grade {
  border: 1px solid var(--border); background: var(--bg-elev); border-radius: 14px; padding: 12px 6px;
  cursor: pointer; display: flex; flex-direction: column; gap: 3px; align-items: center; transition: .16s; color: var(--text);
}
.grade b { font-size: .98rem; }
.grade small { font-size: .72rem; color: var(--text-soft); }
.grade:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.grade.again { border-top: 3px solid var(--again); }
.grade.hard  { border-top: 3px solid var(--hard); }
.grade.good  { border-top: 3px solid var(--good); }
.grade.easy  { border-top: 3px solid var(--easy); }

.empty-state { text-align: center; padding: 50px 16px; }
.empty-emoji { font-size: 3rem; }
.empty-state h2 { margin: 8px 0; }
.empty-state p { color: var(--text-soft); max-width: 40ch; margin: 0 auto 18px; }

/* ---------- Browse ---------- */
.browse-toolbar { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 12px; }
.search, .select {
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  padding: 11px 14px; border-radius: 12px; font-size: .95rem; font-family: inherit;
}
.search { flex: 1 1 260px; }
.browse-count { color: var(--text-soft); font-size: .85rem; margin: 0 0 12px; }
.word-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 12px; }
.word-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 14px 16px; box-shadow: var(--shadow); transition: .16s; position: relative;
}
.word-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }
.wc-head { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; }
.wc-word { font-weight: 800; font-size: 1.12rem; }
.wc-lvl { font-size: .68rem; font-weight: 800; color: var(--accent); }
.wc-en { color: var(--text-soft); margin: 3px 0 8px; }
.wc-ex { font-size: .85rem; font-style: italic; color: var(--text-soft); border-left: 2px solid var(--border); padding-left: 9px; }
.wc-foot { margin-top: 10px; display: flex; justify-content: space-between; align-items: center; }
.wc-cat { font-size: .68rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-soft); }
.mini-link { font-size: .72rem; font-weight: 700; text-decoration: none; color: var(--accent); }

/* ---------- Stats ---------- */
.stat-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); gap: 12px; margin-bottom: 26px; }
.stat-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 18px; text-align: center; box-shadow: var(--shadow); }
.stat-num { display: block; font-size: 2rem; font-weight: 800; letter-spacing: -.03em; }
.stat-label { color: var(--text-soft); font-size: .8rem; }
.view h3 { margin: 22px 0 12px; }
.level-progress { display: flex; flex-direction: column; gap: 12px; }
.lp-row { display: grid; grid-template-columns: 44px 1fr 70px; gap: 12px; align-items: center; }
.lp-name { font-weight: 800; }
.lp-bar { height: 12px; background: var(--bg-elev); border-radius: 999px; overflow: hidden; border: 1px solid var(--border); }
.lp-fill { height: 100%; border-radius: 999px; transition: width .5s; }
.lp-val { font-size: .8rem; color: var(--text-soft); text-align: right; }
.box-chart { display: grid; grid-template-columns: repeat(6, 1fr); gap: 8px; align-items: end; height: 150px; }
.box-col { display: flex; flex-direction: column; align-items: center; gap: 6px; height: 100%; justify-content: flex-end; }
.box-bar { width: 100%; background: linear-gradient(var(--accent), var(--accent-2)); border-radius: 8px 8px 0 0; min-height: 4px; transition: height .5s; }
.box-lab { font-size: .68rem; color: var(--text-soft); }

/* ---------- Settings ---------- */
.setting-block { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 20px; margin-bottom: 16px; box-shadow: var(--shadow); }
.setting-block h3 { margin: 0 0 6px; }
.setting-block.danger { border-color: color-mix(in srgb, var(--again) 40%, var(--border)); }
.muted { color: var(--text-soft); font-size: .9rem; line-height: 1.5; }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 12px; }
.io-msg { font-size: .85rem; margin: 10px 0 0; color: var(--good); min-height: 1em; }
#newLimit { width: 220px; vertical-align: middle; accent-color: var(--accent); }
#newLimitVal { font-weight: 800; margin-left: 8px; }

/* ---------- Grammar ---------- */
.grammar-head { margin-bottom: 16px; }
.grammar-head h2 { margin: 0 0 4px; }
.grammar-list { display: flex; flex-direction: column; gap: 10px; }
.gram-item { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); box-shadow: var(--shadow); overflow: hidden; }
.gram-item summary { cursor: pointer; padding: 15px 18px; font-weight: 700; font-size: 1.02rem; list-style: none; display: flex; justify-content: space-between; align-items: center; }
.gram-item summary::-webkit-details-marker { display: none; }
.gram-item summary::after { content: "+"; color: var(--accent); font-weight: 800; font-size: 1.2rem; }
.gram-item[open] summary::after { content: "–"; }
.gram-body { padding: 0 18px 16px; color: var(--text); line-height: 1.6; }
.gram-body p { margin: 8px 0; color: var(--text-soft); }
.gram-ul { margin: 8px 0; padding-left: 20px; color: var(--text-soft); }
.gram-ul li { margin: 4px 0; }
.gram-ex { display: flex; flex-wrap: wrap; gap: 4px 14px; padding: 9px 12px; margin: 8px 0; background: color-mix(in srgb, var(--accent) 7%, transparent); border-left: 3px solid var(--accent); border-radius: 8px; }
.gex-lb { font-weight: 700; }
.gex-en { color: var(--text-soft); }
.gram-tip { margin: 10px 0; padding: 9px 12px; background: color-mix(in srgb, var(--hard) 14%, transparent); border-radius: 8px; font-size: .9rem; }
.gram-table-wrap { overflow-x: auto; margin: 10px 0; }
.gram-table { border-collapse: collapse; width: 100%; font-size: .92rem; }
.gram-table th, .gram-table td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; }
.gram-table th { background: var(--bg-elev); font-weight: 700; }

/* ---------- Resources ---------- */
.res-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.res-card { display: block; text-decoration: none; color: inherit; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 16px 18px; box-shadow: var(--shadow); transition: .16s; }
.res-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); border-color: color-mix(in srgb, var(--accent) 40%, var(--border)); }
.res-top { display: flex; justify-content: space-between; align-items: flex-start; gap: 8px; }
.res-name { font-weight: 800; font-size: 1.04rem; line-height: 1.2; }
.res-go { color: var(--accent); font-weight: 800; }
.res-tag { display: inline-block; margin: 6px 0; font-size: .68rem; text-transform: uppercase; letter-spacing: .06em; font-weight: 800; color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent); padding: 3px 9px; border-radius: 999px; }
.res-desc { margin: 6px 0 0; color: var(--text-soft); font-size: .9rem; line-height: 1.5; }

/* ---------- Toast ---------- */
.toast {
  position: fixed; left: 50%; bottom: 26px; transform: translateX(-50%) translateY(20px);
  background: var(--text); color: var(--bg); padding: 12px 20px; border-radius: 12px;
  box-shadow: var(--shadow-lg); font-weight: 600; font-size: .9rem; opacity: 0; transition: .25s; z-index: 80;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

@media (max-width: 620px) {
  .brand-sub { display: none; }
  .tabs { order: 3; width: 100%; margin: 0; justify-content: space-between; }
  .topbar { flex-wrap: wrap; }
  .grade small { display: none; }
}
@media (prefers-reduced-motion: reduce) {
  .flashcard-inner { transition: none; }
  * { animation: none !important; }
}