:root {
  --bg: #0f172a;
  --bg2: #1e293b;
  --card: #1e293b;
  --card2: #273449;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --line: #334155;
  --accent: #f59e0b;
  --accent-ink: #1f1300;
  --good: #22c55e;
  --bad: #ef4444;
  --radius: 16px;
  color-scheme: dark light;
}
@media (prefers-color-scheme: light) {
  :root {
    --bg: #f1f5f9; --bg2: #e2e8f0; --card: #ffffff; --card2: #f8fafc;
    --text: #0f172a; --muted: #64748b; --line: #e2e8f0; --accent-ink: #1f1300;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: linear-gradient(160deg, var(--bg), var(--bg2));
  color: var(--text);
  min-height: 100vh;
  min-height: 100dvh;
  -webkit-font-smoothing: antialiased;
}
#app { min-height: 100dvh; display: grid; place-items: start center; }

.screen {
  width: 100%;
  max-width: 620px;
  padding: clamp(1rem, 4vw, 2rem);
  padding-bottom: calc(2rem + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  animation: fade .22s ease;
}
@keyframes fade { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }
.loading { color: var(--muted); padding: 4rem 0; text-align: center; }

/* hero */
.hero { text-align: center; margin-top: clamp(1rem, 5vw, 3rem); }
.hero h1 { font-size: clamp(2rem, 7vw, 2.8rem); margin: 0; letter-spacing: -0.03em; }
.tagline { color: var(--muted); margin: 0.35rem 0 0; }

/* panel */
.panel { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 1rem; display: flex; flex-direction: column; gap: 1rem; }
.row { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.field { flex: 1; min-width: 140px; display: flex; flex-direction: column; gap: 0.35rem; font-size: 0.8rem; color: var(--muted); }
select {
  appearance: none; width: 100%; padding: 0.6rem 0.75rem; border-radius: 10px;
  background: var(--card2); color: var(--text); border: 1px solid var(--line); font-size: 0.95rem;
}

.toggle { display: flex; align-items: center; gap: 0.6rem; margin: 0.9rem 0 0.2rem; font-size: 0.85rem; color: var(--muted); cursor: pointer; }
.toggle input { width: 1.1rem; height: 1.1rem; accent-color: var(--accent); flex: none; }
.toggle b { color: var(--text); font-weight: 600; }

.chips { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.chip {
  display: inline-flex; align-items: center; gap: 0.4rem; padding: 0.5rem 0.8rem;
  border-radius: 999px; border: 1px solid var(--line); background: transparent; color: var(--muted);
  font-size: 0.9rem; cursor: pointer; transition: all .15s;
}
.chip .chip-ico { font-size: 1.05rem; }
.chip.on { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); font-weight: 600; }
.chip:active { transform: scale(0.97); }

/* stats */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0.6rem; }
.summary .stats { grid-template-columns: repeat(3, 1fr); }
.stat { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 0.8rem 0.4rem; text-align: center; }
.stat b { display: block; font-size: 1.4rem; }
.stat span { font-size: 0.72rem; color: var(--muted); }
.stat.streak b { color: var(--accent); }
@media (max-width: 430px) { .stat b { font-size: 1.15rem; } }

/* buttons */
.cta {
  border: none; border-radius: 12px; padding: 0.95rem 1.25rem; font-size: 1.05rem; font-weight: 600;
  background: var(--accent); color: var(--accent-ink); cursor: pointer; width: 100%; transition: transform .1s, opacity .15s;
}
.cta:hover { opacity: 0.94; }
.cta:active { transform: scale(0.99); }
.cta:disabled { background: var(--card2); color: var(--muted); cursor: default; }

.tools { display: flex; gap: 1rem; justify-content: center; align-items: center; margin-top: 0.25rem; }
.link { background: none; border: none; color: var(--muted); font-size: 0.85rem; cursor: pointer; text-decoration: underline; padding: 0.3rem; }
.link.danger { color: var(--bad); }

/* study card */
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: clamp(1.2rem, 5vw, 2rem); display: flex; flex-direction: column; gap: 1rem; align-items: center; text-align: center;
}
.badge {
  align-self: center; font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--muted); border: 1px solid var(--line); border-radius: 999px; padding: 0.2rem 0.6rem;
}
.badge.rung1 { color: #38bdf8; border-color: #38bdf8; }
.badge.rung2 { color: #a78bfa; border-color: #a78bfa; }
.badge.rung3 { color: var(--accent); border-color: var(--accent); }
.prompt { font-size: clamp(1.7rem, 6vw, 2.3rem); font-weight: 700; letter-spacing: -0.02em; display: flex; align-items: center; gap: 0.5rem; flex-wrap: wrap; justify-content: center; }
.prompt.cloze { font-size: clamp(1.15rem, 4vw, 1.5rem); font-weight: 600; line-height: 1.5; }
.cloze-en { margin-top: 0.5rem; text-align: center; font-size: 0.9rem; color: var(--muted); font-style: italic; }
.gloss { color: var(--muted); font-size: 1.1rem; }
.example { background: var(--card2); border-radius: 10px; padding: 0.75rem 1rem; font-size: 0.95rem; line-height: 1.5; }
.example i { color: var(--text); font-style: italic; }
.example span { color: var(--muted); }
.example.tip { margin-top: 0.25rem; }
.note { font-size: 0.82rem; color: var(--muted); background: var(--card2); border-radius: 10px; padding: 0.6rem 0.8rem; }

.speak { background: none; border: none; cursor: pointer; font-size: 1.1rem; opacity: 0.75; padding: 0.1rem; }
.speak:hover { opacity: 1; }

/* options */
.options { display: grid; gap: 0.6rem; width: 100%; }
.option {
  padding: 0.85rem 1rem; border-radius: 12px; border: 1px solid var(--line); background: var(--card2);
  color: var(--text); font-size: 1.05rem; cursor: pointer; transition: transform .1s, border-color .15s, background .15s;
}
.option:hover { border-color: var(--accent); }
.option:active { transform: scale(0.98); }

.type-form { display: flex; gap: 0.6rem; width: 100%; flex-wrap: wrap; }
#type-input {
  flex: 1; min-width: 0; padding: 0.85rem 1rem; border-radius: 12px; border: 1px solid var(--line);
  background: var(--card2); color: var(--text); font-size: 1.1rem; text-align: center;
}
.type-form .cta { width: auto; flex: 0 0 auto; }

.tip-btn { background: none; border: 1px dashed var(--line); color: var(--muted); border-radius: 10px; padding: 0.55rem 0.9rem; cursor: pointer; font-size: 0.88rem; }
.tip-btn:hover { border-color: var(--accent); color: var(--text); }
.q-hints { display: flex; gap: 0.5rem; flex-wrap: wrap; justify-content: center; align-items: center; width: 100%; }
.q-hints .tip-btn { flex: 1 1 auto; }
.guess-btn { width: 100%; background: none; border: 1px dashed var(--line); color: var(--muted); border-radius: 10px; padding: 0.55rem 0.9rem; cursor: pointer; font-size: 0.88rem; transition: all .15s; }
.guess-btn:hover { border-color: var(--accent); color: var(--text); }
.guess-btn.on { background: var(--accent); color: var(--accent-ink); border-style: solid; border-color: var(--accent); font-weight: 600; }
.note.practice { color: var(--accent); }

/* feedback */
.feedback { border-width: 2px; }
.feedback.good { border-color: var(--good); }
.feedback.bad { border-color: var(--bad); }
.verdict { font-size: 1.3rem; font-weight: 700; }
.feedback.good .verdict { color: var(--good); }
.feedback.bad .verdict { color: var(--bad); }
.given { color: var(--muted); font-size: 0.9rem; }
.given s { color: var(--bad); }
.answer { font-size: 1.6rem; font-weight: 700; display: flex; gap: 0.5rem; align-items: center; }

/* progress bar */
.progress { position: relative; height: 8px; background: var(--card2); border-radius: 999px; overflow: hidden; }
.progress-fill { height: 100%; background: var(--accent); border-radius: 999px; transition: width .3s ease; }
.progress-label { position: absolute; right: 0; top: 12px; font-size: 0.72rem; color: var(--muted); }
.study .progress { margin-bottom: 0.5rem; }