:root {
  --bg: #f6f7f9; --card: #fff; --ink: #1c2330; --muted: #5d6675; --line: #dfe3ea;
  --accent: #0d6efd; --accent-ink: #fff; --ok: #1a7f37; --ok-bg: #e6f4ea; --bad: #b42318; --bad-bg: #fdecea;
  --warn: #9a6700; --warn-bg: #fff8e1; --code-bg: #0f172a; --code-ink: #e2e8f0;
  --core: #0d6efd; --stretch: #7c3aed; --boss: #c2410c;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; color: var(--ink); background: var(--bg); }
a { color: var(--accent); }
h1 { font-size: 1.7rem; margin: .2rem 0 .6rem; }
h2 { font-size: 1.25rem; margin: 1.2rem 0 .5rem; }
h3 { font-size: 1.05rem; margin: 1rem 0 .4rem; }
code, pre, .code { font-family: ui-monospace, "JetBrains Mono", Menlo, Consolas, monospace; }
code { background: #eef1f5; padding: .05em .3em; border-radius: 4px; font-size: .95em; }
pre { background: var(--code-bg); color: var(--code-ink); padding: .8rem 1rem; border-radius: 8px; overflow-x: auto; font-size: .95rem; line-height: 1.45; }
pre code { background: none; padding: 0; color: inherit; }
table { border-collapse: collapse; width: 100%; }
th, td { text-align: left; padding: .4rem .6rem; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-weight: 600; color: var(--muted); font-size: .9rem; }
.theory table { margin: .6rem 0 1rem; }
.theory blockquote { margin: .8rem 0; padding: .4rem 1rem; border-left: 4px solid var(--accent); background: #eef4ff; }

header.top { display: flex; align-items: center; justify-content: space-between; padding: .6rem 1.2rem; background: var(--card); border-bottom: 1px solid var(--line); }
header.top .brand { font-weight: 700; text-decoration: none; color: var(--ink); font-size: 1.1rem; }
header.top nav { display: flex; gap: 1rem; align-items: center; }
header.top nav a { text-decoration: none; }
.who { color: var(--muted); }
.inline { display: inline; }
button.link { background: none; border: 0; color: var(--accent); cursor: pointer; font: inherit; padding: 0; }

main.wrap { max-width: 1200px; margin: 0 auto; padding: 1.2rem; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 1.2rem 1.4rem; margin-bottom: 1.2rem; }
.card > h1:first-child, .card > h2:first-child { margin-top: 0; }
.narrow { max-width: 420px; margin: 3rem auto; }
.muted { color: var(--muted); }
.small { font-size: .85rem; }
.nowrap { white-space: nowrap; }
.error { color: var(--bad); background: var(--bad-bg); padding: .5rem .8rem; border-radius: 8px; }
.error-box { border-color: var(--bad); }
.notice { background: var(--warn-bg); border-color: #f5d76e; }
.ok { color: var(--ok); }
.crumbs { color: var(--muted); font-size: .9rem; margin: 0 0 .2rem; }
.theme { font-size: 1.1rem; color: var(--muted); font-style: italic; margin-top: 0; }
.row { display: flex; gap: .6rem; align-items: center; flex-wrap: wrap; }
.row.between { justify-content: space-between; }
.actions { display: flex; gap: .4rem; flex-wrap: wrap; }
.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 1.2rem; }
.scroll { overflow-x: auto; }

label { display: block; margin: .6rem 0; font-weight: 500; }
input[type=text], input[type=password], input:not([type]), textarea { width: 100%; padding: .5rem .6rem; border: 1px solid var(--line); border-radius: 8px; font: inherit; margin-top: .2rem; }
textarea { resize: vertical; }
button, .btn { display: inline-block; padding: .45rem .9rem; border: 1px solid var(--line); border-radius: 8px; background: #fff; color: var(--ink); font: inherit; cursor: pointer; text-decoration: none; }
button:hover, .btn:hover { background: #f0f3f7; }
.primary, button.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.primary:hover, button.primary:hover { background: #0b5ed7; }
.check { background: var(--ok); color: #fff; border-color: var(--ok); }
.check:hover { background: #166b2e; }
.btn.small { padding: .25rem .6rem; font-size: .85rem; }
.danger { color: var(--bad); }
.kbd, kbd { font-size: .75em; opacity: .8; border: 1px solid currentColor; border-radius: 4px; padding: 0 .3em; margin-left: .3em; }

ul.tasks { list-style: none; padding: 0; margin: .4rem 0; }
ul.tasks li { display: flex; gap: .6rem; align-items: center; padding: .35rem 0; border-bottom: 1px solid var(--line); }
ul.tasks li:last-child { border-bottom: 0; }
.tier { font-size: .72rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; padding: .1rem .45rem; border-radius: 999px; color: #fff; background: var(--core); }
.tier.stretch { background: var(--stretch); }
.tier.boss { background: var(--boss); }
.status { margin-left: auto; font-size: .85rem; color: var(--muted); }
.status.ok { color: var(--ok); font-weight: 600; }

.lesson-grid { display: grid; grid-template-columns: minmax(0, 2fr) minmax(280px, 1fr); gap: 1.2rem; align-items: start; }
.lesson .theory h2 { border-top: 1px solid var(--line); padding-top: 1rem; margin-top: 1.6rem; }
.side { position: sticky; top: 1rem; }

.task-grid { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 1.2rem; align-items: start; }
.statement h1 { display: flex; gap: .6rem; align-items: center; font-size: 1.4rem; }
.test-spec { margin: .4rem 0 .8rem; }
.test-spec pre { margin: .2rem 0 .4rem; }
.editor-pane { position: sticky; top: 1rem; }
.toolbar { margin-bottom: .6rem; }
textarea.code { width: 100%; min-height: 340px; background: var(--code-bg); color: var(--code-ink); border: 0; border-radius: 8px; padding: .8rem 1rem; font-size: 15px; line-height: 1.5; tab-size: 4; white-space: pre; overflow: auto; }
textarea.code.small { min-height: 60px; }
textarea.code:focus { outline: 2px solid var(--accent); }
details.stdin { margin: .5rem 0; }
details.stdin summary { cursor: pointer; color: var(--muted); font-size: .9rem; }
.output { margin-top: .6rem; }
.output pre { margin: .3rem 0; white-space: pre-wrap; word-break: break-all; }
.verdict { font-weight: 700; padding: .5rem .8rem; border-radius: 8px; margin: .4rem 0; }
.verdict.ok { background: var(--ok-bg); color: var(--ok); }
.verdict.bad { background: var(--bad-bg); color: var(--bad); }
.verdict.warn { background: var(--warn-bg); color: var(--warn); }
.test { border: 1px solid var(--line); border-radius: 8px; padding: .5rem .8rem; margin: .4rem 0; }
.test.ok { border-color: #9fd3ad; }
.test.bad { border-color: #f1aeb5; }
.test .msg { white-space: pre-wrap; margin: .3rem 0; }
.test .cols { display: grid; grid-template-columns: 1fr 1fr; gap: .6rem; }
.hints { margin-top: 1.2rem; border-top: 1px solid var(--line); padding-top: .6rem; }
.hint { background: var(--warn-bg); border-radius: 8px; padding: .5rem .8rem; margin: .4rem 0; }
.hint pre { background: #fff3c4; color: var(--ink); }

.grid td.cell { text-align: center; font-weight: 600; }
.grid td.ok { background: var(--ok-bg); color: var(--ok); }
.grid td.tried { background: #eef1f5; }
.grid td.stuck, .cell.stuck { background: var(--bad-bg); color: var(--bad); }
.cell.stuck { padding: 0 .4rem; border-radius: 4px; }

.card.locked { opacity: .7; background: #f1f3f6; }
.modules td.cell { text-align: left; font-weight: 400; }
.modules .class-row td { background: #f6f7f9; }
.modules select { font: inherit; font-size: .85rem; padding: .2rem .3rem; border: 1px solid var(--line); border-radius: 6px; background: #fff; max-width: 100%; }
.modules th { min-width: 180px; }

/* ---- projector mode ---- */
body.bare { background: #0b1220; color: #eef2f7; }
main.present { min-height: 100vh; padding: 0 0 3.2rem; }
.deck .slide { display: none; min-height: calc(100vh - 3.2rem); padding: 3rem 6vw; font-size: clamp(1.3rem, 2.4vw, 2.1rem); line-height: 1.5; }
.deck .slide.active, .deck.all .slide { display: block; }
.deck.all .slide { min-height: 0; border-bottom: 1px solid #263246; }
.slide h1 { font-size: clamp(2.2rem, 5vw, 4rem); line-height: 1.15; margin: .2em 0 .3em; }
.slide h2 { font-size: clamp(1.8rem, 4vw, 3rem); margin: 0 0 .6em; color: #8ec5ff; }
.slide .kicker { text-transform: uppercase; letter-spacing: .1em; color: #8ec5ff; margin: 0; }
.slide .theme { color: #c6d0dd; font-size: 1.1em; }
.slide pre { font-size: .95em; padding: .8em 1em; background: #111a2e; border: 1px solid #263246; }
.slide code { background: #1a2540; color: #ffd28a; }
.slide pre code { color: inherit; }
.slide table { font-size: .9em; }
.slide th, .slide td { border-bottom: 1px solid #263246; padding: .3em .6em; }
.slide blockquote { border-left: 6px solid #8ec5ff; background: #111a2e; padding: .3em 1em; margin: .6em 0; }
.slide a { color: #8ec5ff; }
.deck-bar { position: fixed; left: 0; right: 0; bottom: 0; height: 3.2rem; display: flex; align-items: center; justify-content: space-between; padding: 0 1.2rem; background: #060b16; color: #9aa7b8; font-size: .95rem; }
.deck-bar a { color: #9aa7b8; text-decoration: none; }
.deck-bar kbd { border-color: #3a4a63; }

@media (max-width: 900px) {
  .lesson-grid, .task-grid, .two-col { grid-template-columns: 1fr; }
  .side, .editor-pane { position: static; }
  header.top { flex-direction: column; gap: .4rem; }
}