:root {
  --bg: #f6f7f5;
  --card: #ffffff;
  --text: #17201d;
  --muted: #5b6763;
  --line: #dfe4e1;
  --brand: #0f766e;
  --brand-ink: #ffffff;
  --brand-soft: #e3f2ef;
  --ok: #15803d;
  --ok-soft: #e6f4ea;
  --bad: #b42318;
  --bad-soft: #fdecea;
  --part: #a15c07;
  --part-soft: #fdf3e2;
  --bio: #2f855a;
  --chem: #6b46c1;
  --phys: #2b6cb0;
  --radius: 14px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101413;
    --card: #181e1c;
    --text: #e8ecea;
    --muted: #a3aeaa;
    --line: #2b3431;
    --brand: #2bb3a3;
    --brand-ink: #06231f;
    --brand-soft: #173330;
    --ok: #4ade80;
    --ok-soft: #14301f;
    --bad: #f87171;
    --bad-soft: #3a1a18;
    --part: #fbbf24;
    --part-soft: #3a2c10;
    --bio: #68d391;
    --chem: #b794f4;
    --phys: #63b3ed;
  }
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  background: var(--bg);
  color: var(--text);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
}

a { color: var(--brand); }

.wrap { max-width: 680px; margin: 0 auto; padding: 12px 16px 32px; }

.top {
  display: flex; align-items: center; justify-content: space-between; gap: 8px;
  max-width: 680px; margin: 0 auto; padding: 12px 16px 4px;
}
.brand { font-weight: 700; color: var(--text); text-decoration: none; font-size: 15px; }
.lang { display: flex; gap: 6px; }

.chip {
  border: 1px solid var(--line); background: var(--card); color: var(--text);
  border-radius: 999px; padding: 4px 10px; font-size: 13px; cursor: pointer;
}
.chip.on { background: var(--brand); border-color: var(--brand); color: var(--brand-ink); }
.chip.subj { cursor: default; font-weight: 600; }
.chip.subj.bio { color: var(--bio); }
.chip.subj.chem { color: var(--chem); }
.chip.subj.phys { color: var(--phys); }

.hero h1 { font-size: 26px; line-height: 1.25; margin: 16px 0 8px; }
.h2 { font-size: 22px; line-height: 1.3; margin: 0 0 8px; }
.lead { font-size: 17px; margin: 0 0 12px; }
.ticks { padding-left: 0; list-style: none; margin: 0 0 16px; }
.ticks li { padding-left: 26px; position: relative; margin: 6px 0; }
.ticks li::before { content: "✓"; position: absolute; left: 4px; color: var(--brand); font-weight: 700; }
.plain { padding-left: 18px; }
.plain li { margin: 8px 0; }

.muted { color: var(--muted); }
.small { font-size: 14px; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px; margin: 12px 0;
}
.card h3 { margin: 0 0 10px; font-size: 18px; }
.center { text-align: center; }

.stack { display: flex; flex-direction: column; gap: 10px; margin: 12px 0; }

.btn {
  appearance: none; border: 1px solid var(--line); background: var(--card); color: var(--text);
  border-radius: 12px; padding: 12px 16px; font-size: 16px; font-weight: 600; cursor: pointer;
  min-height: 48px;
}
.btn.primary { background: var(--brand); border-color: var(--brand); color: var(--brand-ink); }
.btn.big { font-size: 18px; min-height: 54px; }
.btn.wide { width: 100%; margin-top: 8px; }
.btn[disabled] { opacity: .45; cursor: default; }

.bar { height: 8px; background: var(--line); border-radius: 999px; overflow: hidden; }
.fill { height: 100%; background: var(--brand); border-radius: 999px; }
.fill.bio { background: var(--bio); }
.fill.chem { background: var(--chem); }
.fill.phys { background: var(--phys); }

.meta { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 8px; margin: 10px 0 0; font-size: 14px; color: var(--muted); }
.clock b { color: var(--text); font-variant-numeric: tabular-nums; }

.q .type { margin: 0 0 6px; font-size: 14px; color: var(--muted); }
.qtext { font-size: 18px; line-height: 1.45; margin: 0 0 14px; font-weight: 600; }
.qtext.small { font-size: 15px; font-weight: 500; }

.opts { display: flex; flex-direction: column; gap: 8px; }
.opt {
  display: flex; gap: 12px; align-items: center; text-align: left; width: 100%;
  border: 2px solid var(--line); background: var(--card); color: var(--text);
  border-radius: 12px; padding: 12px; font-size: 16px; cursor: pointer; min-height: 52px;
}
.opt .let {
  flex: 0 0 30px; height: 30px; border-radius: 50%; border: 2px solid var(--line);
  display: inline-flex; align-items: center; justify-content: center; font-weight: 700;
}
.opt.on { border-color: var(--brand); background: var(--brand-soft); }
.opt.on .let { background: var(--brand); border-color: var(--brand); color: var(--brand-ink); }

.rightlist { list-style: none; padding: 0; margin: 0 0 12px; display: grid; gap: 4px; }
.rightlist li { padding: 6px 10px; border-radius: 8px; background: var(--brand-soft); }
.rightlist b { margin-right: 6px; }
.mrows { display: flex; flex-direction: column; gap: 10px; }
.mrow { border: 1px solid var(--line); border-radius: 12px; padding: 10px; }
.mleft { margin-bottom: 8px; }
.mbtns { display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; }
.mb {
  border: 2px solid var(--line); background: var(--card); color: var(--text); border-radius: 10px;
  min-height: 44px; font-size: 17px; font-weight: 700; cursor: pointer;
}
.mb.on { border-color: var(--brand); background: var(--brand); color: var(--brand-ink); }

.numwrap { display: block; }
.num {
  width: 100%; font-size: 26px; letter-spacing: 6px; text-align: center; padding: 12px;
  border: 2px solid var(--line); border-radius: 12px; background: var(--card); color: var(--text);
  font-variant-numeric: tabular-nums;
}
.num:focus { outline: none; border-color: var(--brand); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

.navrow { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 12px 0; }

.palette { margin: 8px 0; }
.palette summary { cursor: pointer; color: var(--muted); padding: 8px 0; }
.grid { display: grid; grid-template-columns: repeat(7, 1fr); gap: 6px; margin: 8px 0; }
.pq {
  border: 1px solid var(--line); background: var(--card); color: var(--text); border-radius: 8px;
  min-height: 40px; font-weight: 600; cursor: pointer;
}
.pq.done { background: var(--brand-soft); border-color: var(--brand); }
.pq.cur { outline: 2px solid var(--brand); outline-offset: 1px; }

.score { text-align: center; }
.eyebrow { margin: 0; color: var(--muted); font-size: 14px; text-transform: uppercase; letter-spacing: .04em; }
.bignum { font-size: 56px; font-weight: 800; line-height: 1.1; margin: 4px 0; color: var(--brand); }
.est { font-weight: 600; }

.srow { margin: 10px 0; }
.slabel { display: flex; justify-content: space-between; font-size: 15px; margin-bottom: 4px; }

.tablewrap { overflow-x: auto; }
table.cut { width: 100%; border-collapse: collapse; font-size: 14px; }
table.cut th, table.cut td { text-align: left; padding: 8px 6px; border-bottom: 1px solid var(--line); vertical-align: top; }
table.cut th { color: var(--muted); font-weight: 600; }
.ok { color: var(--ok); font-weight: 600; }
.gap { color: var(--part); font-weight: 600; }

.weak { padding-left: 20px; }
.weak li { margin: 6px 0; }

.rev { border: 1px solid var(--line); border-radius: 12px; margin: 8px 0; overflow: hidden; }
.rev summary {
  display: flex; align-items: center; gap: 8px; padding: 10px 12px; cursor: pointer; list-style: none; font-size: 14px;
}
.rev summary::-webkit-details-marker { display: none; }
.rev summary .pts { margin-left: auto; color: var(--muted); font-variant-numeric: tabular-nums; }
.badge { border-radius: 999px; padding: 2px 8px; font-size: 12px; font-weight: 700; white-space: nowrap; }
.badge.ok { background: var(--ok-soft); color: var(--ok); }
.badge.bad { background: var(--bad-soft); color: var(--bad); }
.badge.part { background: var(--part-soft); color: var(--part); }
.revbody { padding: 0 12px 12px; border-top: 1px solid var(--line); }
.explain { background: var(--brand-soft); border-radius: 10px; padding: 10px 12px; margin: 8px 0; }

.form { display: flex; flex-direction: column; gap: 10px; margin-top: 10px; }
.roles { border: 0; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 8px 16px; }
.roles legend { font-weight: 600; margin-bottom: 6px; padding: 0; }
.radio { display: inline-flex; align-items: center; gap: 6px; min-height: 36px; }
.fld { display: flex; flex-direction: column; gap: 4px; font-size: 14px; }
.fld input, .fld select {
  font-size: 16px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px;
  background: var(--card); color: var(--text); min-height: 46px;
}
.chk { display: flex; gap: 10px; align-items: flex-start; font-size: 14px; }
.chk input { margin-top: 3px; width: 20px; height: 20px; flex: 0 0 20px; }
.hp { position: absolute; left: -9999px; width: 1px; height: 1px; opacity: 0; }
.err { color: var(--bad); min-height: 1em; margin: 0; font-size: 14px; }
.okmsg { background: var(--ok-soft); color: var(--ok); border-radius: 10px; padding: 10px 12px; font-weight: 600; }

.foot {
  max-width: 680px; margin: 0 auto; padding: 8px 16px 32px; color: var(--muted); font-size: 13px;
  display: flex; flex-direction: column; gap: 4px;
}
.demo { color: var(--part); }

.toast {
  position: fixed; left: 50%; bottom: 24px; transform: translateX(-50%);
  background: var(--text); color: var(--bg); padding: 10px 16px; border-radius: 999px; font-size: 14px; z-index: 10;
}

@media (min-width: 560px) {
  .stack { flex-direction: row; }
  .stack .btn { flex: 1; }
}

/* ---------- Hablox interactive models ---------- */
.btn.small { min-height: 40px; font-size: 14px; padding: 8px 12px; margin: 4px 0; }
.mbox:empty { display: none; }
.model { border: 1px solid var(--line); border-radius: 12px; padding: 12px; margin: 8px 0; background: var(--bg); }
.msvg { width: 100%; max-height: 260px; display: block; margin: 4px auto 8px; }
.msvg.short { max-height: 140px; }
.msvg .axis { stroke: var(--muted); stroke-width: 1.5; }
.msvg .tick { fill: var(--muted); font-size: 11px; }
.msvg .trail { stroke: var(--brand); stroke-width: 2; stroke-dasharray: 4 4; }
.msvg .ground { stroke: var(--text); stroke-width: 2; }
.msvg .ball { fill: var(--brand); }
.msvg .wire { stroke: var(--text); stroke-width: 2; }
.msvg .res { fill: var(--brand-soft); stroke: var(--brand); stroke-width: 2; }
.msvg .rlabel { fill: var(--text); font-size: 12px; font-weight: 700; }
.mlabel { display: flex; flex-direction: column; gap: 4px; margin: 8px 0; font-size: 15px; }
.mlabel input[type="range"] { width: 100%; accent-color: var(--brand); min-height: 32px; }
.mnums { display: flex; flex-wrap: wrap; gap: 6px 16px; font-size: 15px; }
.mnums b { font-variant-numeric: tabular-nums; }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; margin: 4px 0 8px; }
.seg button { border: 0; background: var(--card); color: var(--text); padding: 8px 14px; font-size: 15px; font-weight: 600; cursor: pointer; min-height: 40px; }
.seg button + button { border-left: 1px solid var(--line); }
.seg button.on { background: var(--brand); color: var(--brand-ink); }
.pgroup { margin: 4px 0; }
.pgrid { border-collapse: collapse; margin: 8px 0; font-size: 18px; }
.pgrid th, .pgrid td { width: 56px; height: 44px; text-align: center; border: 1px solid var(--line); }
.pgrid th { color: var(--muted); }
.pgrid td.dominant { background: var(--brand-soft); }
.pgrid td.recessive { background: var(--part-soft); color: var(--part); font-weight: 700; }

/* ---------- landing, teachers, contact ---------- */
.steps { padding-left: 22px; margin: 0; }
.steps li { margin: 8px 0; }
.whogrid { display: grid; gap: 10px; }
.whocard {
  display: flex; flex-direction: column; gap: 2px; padding: 12px 14px; border: 1px solid var(--line);
  border-radius: 12px; text-decoration: none; color: var(--text); background: var(--bg);
}
.whocard b { color: var(--brand); font-size: 17px; }
.whocard span { font-size: 14px; color: var(--muted); }
.linkbox { margin: 12px 0; padding: 12px; border-radius: 12px; background: var(--brand-soft); }
.linkbox code { display: block; word-break: break-all; font-size: 15px; margin-bottom: 4px; }
.linkbox .btn { text-align: center; text-decoration: none; display: inline-flex; align-items: center; justify-content: center; }
.fld textarea {
  font: inherit; font-size: 16px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px;
  background: var(--card); color: var(--text); resize: vertical;
}
@media (min-width: 560px) { .whogrid { grid-template-columns: repeat(3, 1fr); } }
.en { margin: 4px 0 0; }
.hero .whogrid { margin: 4px 0 12px; }