:root {
  --bg: #fafafa;
  --surface: #ffffff;
  --subtle: #f4f4f5;
  --line: #e6e6e9;
  --line-strong: #d4d4d8;
  --text: #18181b;
  --muted: #71717a;
  --accent: #4f46e5;
  --accent-soft: #eef0ff;
  --accent-ink: #ffffff;
  --good: #059669;
  --good-soft: #e8f7f1;
  --warn: #d97706;
  --warn-soft: #fff6e6;
  --bad: #dc2626;
  --code-bg: #f6f6f8;
  --k: #7c3aed; --s: #0f766e; --n: #c2410c; --c: #9ca3af;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(24,24,27,.04), 0 4px 16px -6px rgba(24,24,27,.08);
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c0c0f; --surface: #141418; --subtle: #1b1b21; --line: #26262d; --line-strong: #3a3a44;
    --text: #f4f4f5; --muted: #9a9aa6; --accent: #8b8cff; --accent-soft: #1d1d3a; --accent-ink: #0c0c0f;
    --good: #34d399; --good-soft: #0f2a22; --warn: #fbbf24; --warn-soft: #2d2410; --bad: #f87171;
    --code-bg: #0f0f13; --k: #c4a5ff; --s: #7ee0c3; --n: #fdba74; --c: #6b6b78;
    --shadow: 0 1px 2px rgba(0,0,0,.4);
  }
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--text); }
body { font-family: Inter, system-ui, -apple-system, "Segoe UI", sans-serif; line-height: 1.6; -webkit-font-smoothing: antialiased; min-height: 100vh; font-size: 15px; }
.bg-glow { display: none; }
button { font: inherit; color: inherit; cursor: pointer; }
.hidden { display: none !important; }

/* ---------- buttons ---------- */
.btn { border: 1px solid var(--line-strong); background: var(--surface); padding: 9px 16px; border-radius: 10px; font-weight: 500; font-size: 14px; transition: background .15s, border-color .15s, transform .1s; }
.btn:hover { background: var(--subtle); }
.btn:active { transform: scale(.98); }
.btn:disabled { opacity: .4; cursor: not-allowed; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
.btn.primary:hover { filter: brightness(1.08); background: var(--accent); }
.btn.ghost { border-color: transparent; background: transparent; color: var(--muted); }
.btn.ghost:hover { background: var(--subtle); color: var(--text); }
.btn.danger { color: var(--bad); }
.btn.lg { padding: 12px 22px; font-size: 15px; border-radius: 12px; }

/* ---------- intro ---------- */
.intro { max-width: 680px; margin: 0 auto; padding: 72px 24px 96px; }
.badge { display: inline-block; padding: 4px 12px; border-radius: 99px; background: var(--accent-soft); color: var(--accent); font-size: 13px; font-weight: 600; }
.intro h1 { font-size: clamp(32px, 5.5vw, 46px); line-height: 1.1; letter-spacing: -.035em; margin: 20px 0 14px; font-weight: 700; }
.grad { color: var(--accent); }
.lead { color: var(--muted); font-size: 17px; margin: 0 0 32px; max-width: 560px; }
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-bottom: 20px; }
.stat { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; }
.stat b { display: block; font-size: 24px; letter-spacing: -.02em; font-weight: 700; }
.stat span { color: var(--muted); font-size: 13px; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 24px; box-shadow: var(--shadow); }
.rules { margin: 0 0 24px; padding: 0; list-style: none; display: grid; gap: 12px; }
.rules li { display: flex; gap: 12px; color: var(--muted); font-size: 14.5px; }
.rules li::before { content: ""; flex: none; width: 6px; height: 6px; margin-top: 9px; border-radius: 50%; background: var(--accent); }
.field label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; font-weight: 500; }
.input, .textarea { width: 100%; background: var(--surface); color: var(--text); border: 1px solid var(--line-strong); border-radius: 10px; padding: 11px 14px; font: inherit; outline: none; transition: border .15s, box-shadow .15s; }
.input:focus, .textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.textarea { resize: vertical; min-height: 96px; }
.textarea.mono { font-family: var(--mono); font-size: 13.5px; line-height: 1.65; tab-size: 4; white-space: pre; overflow: auto; min-height: 170px; background: var(--code-bg); }
.textarea.big { min-height: 300px; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }

/* ---------- layout ---------- */
.shell { display: grid; grid-template-columns: 280px 1fr; min-height: 100vh; }
.side { position: sticky; top: 0; height: 100vh; overflow: auto; padding: 26px 20px; border-right: 1px solid var(--line); background: var(--surface); }
.brand { font-weight: 700; letter-spacing: -.01em; font-size: 16px; }
.brand small { display: block; color: var(--muted); font-weight: 400; font-size: 13px; letter-spacing: 0; }
.progress { height: 4px; background: var(--subtle); border-radius: 99px; overflow: hidden; margin: 18px 0 8px; }
.progress i { display: block; height: 100%; width: 0; background: var(--accent); border-radius: 99px; transition: width .3s; }
.meta-line { display: flex; justify-content: space-between; color: var(--muted); font-size: 12.5px; }
.sec { margin-top: 22px; }
.sec h4 { margin: 0 0 8px; font-size: 12px; font-weight: 600; color: var(--muted); display: flex; gap: 8px; align-items: center; }
.sec h4 i { width: 6px; height: 6px; border-radius: 50%; display: inline-block; }
.pal { display: flex; flex-wrap: wrap; gap: 5px; }
.dot { width: 32px; height: 32px; border-radius: 8px; border: 1px solid transparent; background: var(--subtle); font-size: 12.5px; font-weight: 500; color: var(--muted); position: relative; padding: 0; transition: .12s; }
.dot:hover { background: var(--line); color: var(--text); }
.dot.done { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.dot.idk { background: var(--subtle); color: var(--muted); text-decoration: line-through; }
.dot.cur { border-color: var(--accent); background: var(--surface); color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); font-weight: 700; }
.dot.flag::after { content: ""; position: absolute; top: 3px; right: 3px; width: 6px; height: 6px; border-radius: 50%; background: var(--warn); }
.side-foot { margin-top: 26px; padding-top: 18px; border-top: 1px solid var(--line); display: grid; gap: 6px; }
.saved { color: var(--muted); font-size: 12px; display: flex; gap: 8px; align-items: center; margin-top: 4px; }
.saved::before { content: ""; width: 6px; height: 6px; border-radius: 50%; background: var(--good); }
.main { padding: 48px clamp(20px, 5vw, 64px) 130px; max-width: 900px; width: 100%; }
.topbar-m { display: none; }

/* ---------- question ---------- */
.qhead { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 22px; }
.chips { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.chip { display: inline-flex; gap: 7px; align-items: center; padding: 3px 10px; border-radius: 99px; font-size: 12.5px; font-weight: 500; background: var(--subtle); color: var(--muted); }
.chip i { width: 6px; height: 6px; border-radius: 50%; }
.chip:first-child { color: var(--text); }
.flagbtn { padding: 7px 12px; font-size: 13px; }
.flagbtn.on { color: var(--warn); border-color: var(--warn); background: var(--warn-soft); }
.prompt { font-size: 20px; font-weight: 600; letter-spacing: -.015em; line-height: 1.4; margin: 0 0 18px; }
pre.code { margin: 0 0 22px; padding: 18px 20px; background: var(--code-bg); border: 1px solid var(--line); border-radius: var(--radius); overflow: auto; font: 400 13.5px/1.7 var(--mono); tab-size: 4; }
pre.code .k { color: var(--k); } pre.code .s { color: var(--s); } pre.code .n { color: var(--n); } pre.code .c { color: var(--c); font-style: italic; }
.opts { display: grid; gap: 8px; margin-bottom: 22px; }
.opt { display: flex; gap: 14px; align-items: flex-start; text-align: left; width: 100%; padding: 13px 16px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--line); transition: .12s; font-size: 15px; }
.opt:hover { border-color: var(--line-strong); background: var(--subtle); }
.opt .l { flex: none; width: 24px; height: 24px; border-radius: 7px; display: grid; place-items: center; font-weight: 600; font-size: 12px; background: var(--subtle); color: var(--muted); }
.opt.sel { border-color: var(--accent); background: var(--accent-soft); box-shadow: 0 0 0 1px var(--accent); }
.opt.sel .l { background: var(--accent); color: var(--accent-ink); }
.opt.multi .l { border-radius: 50%; }
.opt .t { padding-top: 1px; }
.opt .t.mono { font-family: var(--mono); font-size: 13.5px; }
.match { display: grid; gap: 8px; margin-bottom: 22px; }
.match .mrow { display: grid; grid-template-columns: minmax(150px, 1fr) 1.4fr; gap: 12px; align-items: center; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 14px; }
.match code { font-family: var(--mono); font-size: 13.5px; }
select.input { appearance: none; background-image: linear-gradient(45deg, transparent 50%, var(--muted) 50%), linear-gradient(135deg, var(--muted) 50%, transparent 50%); background-position: calc(100% - 18px) 50%, calc(100% - 13px) 50%; background-size: 5px 5px; background-repeat: no-repeat; padding-right: 34px; }
.sub { margin: 20px 0 8px; font-size: 13px; color: var(--muted); font-weight: 500; }
.conf { display: flex; gap: 6px; flex-wrap: wrap; }
.pill { padding: 6px 14px; border-radius: 99px; border: 1px solid var(--line-strong); background: var(--surface); font-size: 13px; font-weight: 500; color: var(--muted); transition: .12s; }
.pill:hover { color: var(--text); background: var(--subtle); }
.pill.on { color: var(--accent-ink); border-color: transparent; font-weight: 600; }
.pill.on.sure { background: var(--good); } .pill.on.maybe { background: var(--accent); } .pill.on.guess { background: var(--warn); } .pill.on.idk { background: var(--muted); }
details.why { margin-top: 4px; }
details.why summary { cursor: pointer; color: var(--muted); font-size: 13.5px; padding: 4px 0; }
details.why summary:hover { color: var(--accent); }
details.why .textarea { margin-top: 8px; }
.qnav { position: fixed; left: 280px; right: 0; bottom: 0; padding: 16px clamp(20px, 5vw, 64px); background: linear-gradient(180deg, transparent, var(--bg) 45%); z-index: 5; }
.qnav .inner { display: flex; justify-content: space-between; width: 100%; max-width: 900px; }

/* ---------- review / done ---------- */
.rv-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 12px; margin: 22px 0; }
.rv-grid .stat b.good { color: var(--good); } .rv-grid .stat b.warn { color: var(--warn); } .rv-grid .stat b.bad { color: var(--bad); }
.list { display: flex; flex-wrap: wrap; gap: 5px; margin-top: 10px; }
.err { color: var(--bad); font-size: 14px; margin-top: 12px; }
.done-wrap { max-width: 560px; margin: 0 auto; padding: 110px 24px; text-align: center; }
.done-wrap .tick { width: 64px; height: 64px; border-radius: 50%; display: grid; place-items: center; margin: 0 auto 24px; font-size: 28px; background: var(--good-soft); color: var(--good); }

.toast { position: fixed; bottom: 90px; left: 50%; transform: translate(-50%, 16px); background: var(--text); color: var(--bg); padding: 10px 16px; border-radius: 10px; opacity: 0; pointer-events: none; transition: .25s; z-index: 50; font-size: 14px; }
.toast.show { opacity: 1; transform: translate(-50%, 0); }
.modal { position: fixed; inset: 0; z-index: 100; background: rgba(0,0,0,.4); display: grid; place-items: center; padding: 20px; }
.modal .box { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 24px; max-width: 400px; width: 100%; box-shadow: 0 20px 50px -12px rgba(0,0,0,.3); }
.modal p { margin: 0 0 20px; font-size: 16px; font-weight: 500; }

/* ---------- responsive ---------- */
@media (max-width: 880px) {
  .shell { grid-template-columns: 1fr; }
  .side { position: fixed; inset: 0 auto 0 0; width: 300px; max-width: 85vw; z-index: 30; transform: translateX(-102%); transition: .25s; height: 100%; }
  .side.open { transform: none; box-shadow: 0 0 0 100vmax rgba(0,0,0,.4); }
  .topbar-m { display: flex; align-items: center; justify-content: space-between; padding: 10px 18px; border-bottom: 1px solid var(--line); position: sticky; top: 0; z-index: 10; background: var(--surface); }
  .qnav { left: 0; }
  .main { padding-top: 28px; }
  .match .mrow { grid-template-columns: 1fr; }
  .prompt { font-size: 18px; }
}