:root {
  --bg: #000;
  --s1: #09090a;
  --s2: #0f0f11;
  --s3: #151517;
  --s4: #1c1c1f;
  --s5: #242428;
  --s6: #2e2e33;
  --line: rgba(255, 255, 255, 0.05);
  --text: #ededf0;
  --soft: #b4b4bc;
  --muted: #85858e;
  --faint: #4f4f57;
  --good: #4ade80;
  --bad: #f87171;
  --lang: #ededf0;
  --lang-ink: #000;
  --radius: 18px;
  --mono: 'JetBrains Mono', ui-monospace, Consolas, monospace;
  --sans: 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 15px;
  line-height: 1.55;
  font-feature-settings: 'tnum' 1, 'cv11' 1;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; border: 0; background: none; cursor: pointer; padding: 0; }
button:focus { outline: none; }
:focus-visible { outline: none; }
::selection { background: rgba(255, 255, 255, 0.14); }
code, pre, .mono { font-family: var(--mono); }
h1, h2, h3, h4 { margin: 0; font-weight: 600; letter-spacing: -0.015em; }
p { margin: 0; }
svg { display: block; }

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--s4); border-radius: 10px; border: 3px solid var(--bg); }
::-webkit-scrollbar-thumb:hover { background: var(--s5); }

.top {
  position: sticky;
  top: 0;
  z-index: 50;
  height: 60px;
  display: flex;
  align-items: center;
  gap: 28px;
  padding: 0 24px;
  background: rgba(0, 0, 0, 0.82);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 600; font-size: 16px; letter-spacing: -0.01em; }
.brand-mark svg { width: 26px; height: 26px; }
.nav { position: relative; display: flex; gap: 2px; background: var(--s2); padding: 4px; border-radius: 12px; }
.nav a { position: relative; z-index: 1; padding: 6px 14px; border-radius: 9px; color: var(--muted); font-size: 14px; font-weight: 500; transition: color 0.2s; }
.nav a:hover { color: var(--soft); }
.nav a.on { color: var(--text); }
.nav-pill { position: absolute; top: 4px; bottom: 4px; left: 0; width: 0; border-radius: 9px; background: var(--s5); transition: transform 0.35s var(--ease), width 0.35s var(--ease), opacity 0.2s; opacity: 0; }
.top-stats { margin-left: auto; display: flex; align-items: center; gap: 10px; }
.chip { display: inline-flex; align-items: center; gap: 7px; height: 32px; padding: 0 12px; border-radius: 10px; background: var(--s2); color: var(--soft); font-size: 13px; font-weight: 500; white-space: nowrap; }
.chip svg { width: 15px; height: 15px; }
.chip.hot { color: #ffb86b; }
.level-chip { gap: 10px; }
.level-chip .bar { width: 64px; height: 5px; border-radius: 4px; background: var(--s5); overflow: hidden; }
.level-chip .bar i { display: block; height: 100%; background: var(--text); border-radius: 4px; transition: width 0.6s var(--ease); }

main { min-height: calc(100vh - 60px); }
.page { max-width: 1180px; margin: 0 auto; padding: 40px 24px 80px; animation: rise 0.45s var(--ease); }
@keyframes rise { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

.glow { position: fixed; inset: 0; pointer-events: none; z-index: -1; background: radial-gradient(900px 520px at 8% -10%, color-mix(in srgb, var(--lang) 9%, transparent), transparent 70%); transition: background 0.6s; }

.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; height: 38px; padding: 0 16px; border-radius: 11px; background: var(--s4); color: var(--text); font-size: 14px; font-weight: 500; white-space: nowrap; transition: background 0.15s, transform 0.1s, opacity 0.15s; user-select: none; }
.btn:hover { background: var(--s5); }
.btn:focus-visible { background: var(--s6); }
.btn:active { transform: scale(0.98); }
.btn svg { width: 16px; height: 16px; }
.btn.primary { background: var(--text); color: #000; }
.btn.primary:hover { background: #fff; }
.btn.lang { background: var(--lang); color: var(--lang-ink); }
.btn.lang:hover { filter: brightness(1.08); }
.btn.quiet { background: transparent; color: var(--muted); }
.btn.quiet:hover { background: var(--s3); color: var(--text); }
.btn.small { height: 30px; padding: 0 11px; font-size: 13px; border-radius: 9px; }
.btn[disabled] { opacity: 0.4; pointer-events: none; }

.eyebrow { font-size: 12px; font-weight: 500; letter-spacing: 0.08em; text-transform: uppercase; color: var(--muted); }
.muted { color: var(--muted); }

.hero { display: flex; align-items: flex-end; justify-content: space-between; gap: 24px; margin-bottom: 32px; }
.hero h1 { font-size: 34px; line-height: 1.15; margin-top: 8px; }
.hero p { color: var(--muted); margin-top: 8px; max-width: 560px; }

.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-bottom: 36px; }
.stat { background: var(--s1); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; }
.stat .k { font-size: 13px; color: var(--muted); }
.stat .v { font-size: 26px; font-weight: 600; margin-top: 4px; letter-spacing: -0.02em; }
.stat .v small { font-size: 14px; color: var(--muted); font-weight: 500; margin-left: 4px; }
.stat .meter { margin-top: 10px; height: 5px; border-radius: 4px; background: var(--s4); overflow: hidden; }
.stat .meter i { display: block; height: 100%; background: var(--text); border-radius: 4px; }

.section-title { display: flex; align-items: baseline; justify-content: space-between; margin: 0 0 14px; }
.section-title h2 { font-size: 18px; }

.courses { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 14px; }
.course-card { position: relative; display: flex; flex-direction: column; gap: 16px; padding: 22px; border-radius: 22px; background: var(--s1); border: 1px solid var(--line); overflow: hidden; transition: background 0.2s, transform 0.2s var(--ease); }
.course-card:hover { background: var(--s2); transform: translateY(-2px); }
.course-card::before { content: ''; position: absolute; inset: 0; background: radial-gradient(380px 180px at 0% 0%, color-mix(in srgb, var(--c) 14%, transparent), transparent 70%); pointer-events: none; }
.course-card .row { display: flex; align-items: center; gap: 14px; }
.lang-mark { width: 44px; height: 44px; border-radius: 13px; display: grid; place-items: center; background: color-mix(in srgb, var(--c) 16%, var(--s2)); color: var(--c); font-family: var(--mono); font-weight: 500; font-size: 15px; flex: none; }
.course-card h3 { font-size: 18px; }
.course-card .tag { font-size: 13px; color: var(--muted); }
.course-card .start { position: absolute; top: 20px; right: 20px; font-size: 12px; font-weight: 500; padding: 4px 10px; border-radius: 8px; background: var(--c); color: #000; }
.progress { height: 6px; border-radius: 4px; background: var(--s4); overflow: hidden; }
.progress i { display: block; height: 100%; border-radius: 4px; background: var(--c, var(--lang)); transition: width 0.8s var(--ease); }
.course-card .foot { display: flex; align-items: center; justify-content: space-between; font-size: 13px; color: var(--muted); }
.course-card .foot b { color: var(--text); font-weight: 500; }

.continue { display: flex; align-items: center; gap: 16px; padding: 18px 20px; border-radius: var(--radius); background: var(--s1); border: 1px solid var(--line); margin-bottom: 36px; transition: background 0.2s; }
.continue:hover { background: var(--s2); }
.continue .grow { flex: 1; min-width: 0; }
.continue .t { font-weight: 500; }
.continue .s { color: var(--muted); font-size: 13px; }

.badge-strip { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 36px; }

.course-head { display: grid; grid-template-columns: 1fr 300px; gap: 32px; align-items: start; }
.course-head h1 { font-size: 34px; display: flex; align-items: center; gap: 14px; margin-top: 10px; }
.course-head .intro { color: var(--soft); margin-top: 10px; max-width: 620px; }
.side { position: sticky; top: 84px; display: flex; flex-direction: column; gap: 12px; }
.panel { background: var(--s1); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; }
.panel h4 { font-size: 13px; color: var(--muted); font-weight: 500; margin-bottom: 8px; }
.panel .big { font-size: 24px; font-weight: 600; }
.next-card .t { font-size: 17px; font-weight: 600; margin: 4px 0 4px; }
.next-card .s { color: var(--muted); font-size: 14px; margin-bottom: 14px; }
.legend { display: flex; flex-direction: column; gap: 8px; font-size: 13px; color: var(--muted); }
.legend span { display: flex; align-items: center; gap: 10px; }
.legend i { width: 12px; height: 12px; border-radius: 50%; }

.tree-wrap { position: relative; margin-top: 28px; padding: 24px 0 40px; border-radius: 26px; background: var(--s1); border: 1px solid var(--line); overflow-x: auto; }
.tree { position: relative; margin: 0 auto; }
.tree svg.edges { position: absolute; inset: 0; overflow: visible; }
.edge { fill: none; stroke: var(--s4); stroke-width: 2.5; stroke-linecap: round; }
.edge.on { stroke: color-mix(in srgb, var(--lang) 55%, transparent); }
.edge.next { stroke: color-mix(in srgb, var(--lang) 24%, transparent); stroke-dasharray: 2 7; }
.node { position: absolute; width: 140px; margin-left: -70px; display: flex; flex-direction: column; align-items: center; gap: 10px; text-align: center; animation: pop 0.5s var(--ease) backwards; }
@keyframes pop { from { opacity: 0; transform: scale(0.85); } to { opacity: 1; transform: none; } }
.node .orb { position: relative; width: 62px; height: 62px; border-radius: 50%; display: grid; place-items: center; background: var(--s3); color: var(--faint); font-family: var(--mono); font-weight: 500; font-size: 17px; transition: transform 0.2s var(--ease), background 0.2s, box-shadow 0.3s; }
.node .orb svg { width: 22px; height: 22px; }
.node .name { position: relative; font-size: 13px; font-weight: 500; color: var(--muted); line-height: 1.3; padding: 3px 8px; border-radius: 8px; background: var(--s1); }
.node.done .orb { background: var(--lang); color: var(--lang-ink); }
.node.done .name { color: var(--soft); }
.node.open .orb { background: color-mix(in srgb, var(--lang) 18%, var(--s2)); color: var(--lang); box-shadow: 0 0 0 8px color-mix(in srgb, var(--lang) 7%, transparent), 0 0 34px color-mix(in srgb, var(--lang) 22%, transparent); }
.node.open .name { color: var(--text); }
.node.open .orb::after { content: ''; position: absolute; inset: -8px; border-radius: 50%; background: color-mix(in srgb, var(--lang) 10%, transparent); animation: breathe 2.8s ease-in-out infinite; z-index: -1; }
@keyframes breathe { 0%, 100% { transform: scale(0.9); opacity: 0.4; } 50% { transform: scale(1.12); opacity: 0.9; } }
.node:not(.locked) { cursor: pointer; }
.node:not(.locked):hover .orb { transform: scale(1.07); }
.node.locked { cursor: not-allowed; }
.node.shake .orb { animation: shake 0.4s; }
@keyframes shake { 20%, 60% { transform: translateX(-4px); } 40%, 80% { transform: translateX(4px); } }
.tip { position: absolute; z-index: 5; width: 240px; padding: 12px 14px; border-radius: 13px; background: var(--s4); font-size: 13px; color: var(--soft); pointer-events: none; opacity: 0; transform: translateY(4px); transition: opacity 0.15s, transform 0.15s; }
.tip.show { opacity: 1; transform: none; }
.tip b { display: block; color: var(--text); font-weight: 500; margin-bottom: 2px; }
.tip .meta { margin-top: 6px; color: var(--muted); font-size: 12px; }

.lesson { display: grid; grid-template-columns: minmax(380px, 1fr) minmax(440px, 1.15fr); height: calc(100vh - 60px); }
.lesson-left { overflow-y: auto; border-right: 1px solid var(--line); }
.lesson-inner { max-width: 640px; margin: 0 auto; padding: 30px 32px 120px; animation: rise 0.45s var(--ease); }
.crumbs { display: flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); }
.crumbs a:hover { color: var(--text); }
.crumbs svg { width: 14px; height: 14px; }
.lesson-inner h1 { font-size: 30px; margin: 12px 0 18px; }
.steps { display: flex; gap: 6px; margin-bottom: 28px; }
.step { display: flex; align-items: center; gap: 8px; height: 32px; padding: 0 12px; border-radius: 10px; background: var(--s2); color: var(--muted); font-size: 13px; font-weight: 500; }
.step i { width: 18px; height: 18px; border-radius: 50%; display: grid; place-items: center; background: var(--s4); font-style: normal; font-size: 11px; }
.step i svg { width: 11px; height: 11px; }
.step.done { color: var(--text); }
.step.done i { background: var(--lang); color: var(--lang-ink); }

.block { margin-bottom: 18px; }
.prose { color: var(--soft); font-size: 15.5px; line-height: 1.7; }
.prose p + p { margin-top: 12px; }
.prose strong { color: var(--text); font-weight: 600; }
.prose code, .task code, .why code, .opt code, .hint code { font-size: 0.88em; padding: 2px 6px; border-radius: 6px; background: var(--s3); color: var(--text); }
.codeblock { border-radius: 14px; background: var(--s1); border: 1px solid var(--line); overflow: hidden; }
.codeblock pre { margin: 0; padding: 14px 16px; font-size: 13.5px; line-height: 1.65; overflow-x: auto; color: #d6d6db; }
.codeblock .out { border-top: 1px solid var(--line); padding: 10px 16px 12px; background: var(--s2); }
.codeblock .out .eyebrow { font-size: 10.5px; margin-bottom: 4px; }
.codeblock .out pre { padding: 0; color: var(--soft); white-space: pre-wrap; }
.tipbox { display: flex; gap: 12px; padding: 14px 16px; border-radius: 14px; background: color-mix(in srgb, var(--lang) 7%, var(--s1)); color: var(--soft); font-size: 14.5px; }
.tipbox svg { width: 18px; height: 18px; flex: none; margin-top: 2px; color: var(--lang); }

.part-title { display: flex; align-items: center; gap: 10px; margin: 40px 0 16px; font-size: 19px; }
.part-title svg { width: 20px; height: 20px; color: var(--lang); flex: none; }
.part-title .count { margin-left: auto; font-size: 13px; color: var(--muted); font-weight: 500; }
.q { padding: 18px; border-radius: 18px; background: var(--s1); border: 1px solid var(--line); margin-bottom: 12px; }
.q .qt { font-weight: 500; margin-bottom: 12px; }
.opts { display: flex; flex-direction: column; gap: 6px; }
.opt { display: flex; align-items: center; gap: 12px; text-align: left; padding: 11px 14px; border-radius: 12px; background: var(--s3); color: var(--soft); font-size: 14.5px; transition: background 0.15s, color 0.15s; }
.opt:hover { background: var(--s4); color: var(--text); }
.opt .key { width: 22px; height: 22px; flex: none; border-radius: 7px; display: grid; place-items: center; background: var(--s5); font-size: 11.5px; font-family: var(--mono); color: var(--muted); }
.opt.right { background: color-mix(in srgb, var(--good) 14%, var(--s2)); color: var(--text); }
.opt.right .key { background: var(--good); color: #000; }
.opt.wrong { background: color-mix(in srgb, var(--bad) 12%, var(--s2)); color: var(--muted); pointer-events: none; }
.opt.wrong .key { background: color-mix(in srgb, var(--bad) 60%, var(--s4)); color: #000; }
.q.solved .opt:not(.right) { opacity: 0.45; pointer-events: none; }
.why { margin-top: 12px; font-size: 14px; color: var(--soft); padding: 10px 14px; border-radius: 11px; background: var(--s2); animation: rise 0.3s var(--ease); }
.why.bad { color: #f3a5a5; }

.task { padding: 18px 20px; border-radius: 18px; background: color-mix(in srgb, var(--lang) 6%, var(--s1)); border: 1px solid var(--line); color: var(--soft); font-size: 15px; line-height: 1.7; }
.task p + p { margin-top: 10px; }
.task strong { color: var(--text); }
.inputs { margin-top: 14px; font-size: 13px; color: var(--muted); }
.inputs pre { margin: 6px 0 0; padding: 10px 12px; border-radius: 10px; background: var(--s2); color: var(--soft); font-size: 13px; }
.help-row { display: flex; gap: 8px; margin-top: 14px; flex-wrap: wrap; }
.hint { display: flex; gap: 12px; margin-top: 10px; padding: 12px 14px; border-radius: 12px; background: var(--s2); color: var(--soft); font-size: 14.5px; animation: rise 0.3s var(--ease); }
.hint .n { flex: none; width: 22px; height: 22px; border-radius: 7px; display: grid; place-items: center; background: var(--s4); font-size: 12px; color: var(--muted); }
.solution { margin-top: 12px; animation: rise 0.3s var(--ease); }
.solution .bar { display: flex; align-items: center; justify-content: space-between; padding: 8px 10px 8px 16px; background: var(--s2); font-size: 13px; color: var(--muted); }

.lesson-right { display: flex; flex-direction: column; min-width: 0; background: var(--s1); }
.ed-bar { display: flex; align-items: center; gap: 8px; height: 54px; padding: 0 14px; border-bottom: 1px solid var(--line); flex: none; }
.ed-bar .file { display: flex; align-items: center; gap: 9px; font-family: var(--mono); font-size: 13px; color: var(--soft); margin-right: auto; }
.ed-bar .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--lang); }
.kbd { font-family: var(--mono); font-size: 11px; color: color-mix(in srgb, var(--lang-ink) 60%, transparent); margin-left: 2px; }
.ed-host { flex: 1 1 60%; min-height: 160px; position: relative; overflow: hidden; }
.ed-host .CodeMirror { position: absolute; inset: 0; height: auto; }
.out-host { flex: 1 1 40%; min-height: 150px; display: flex; flex-direction: column; border-top: 1px solid var(--line); background: var(--bg); }
.out-tabs { display: flex; align-items: center; gap: 4px; padding: 8px 12px 0; flex: none; }
.out-tab { padding: 6px 12px; border-radius: 9px; font-size: 13px; font-weight: 500; color: var(--muted); }
.out-tab.on { background: var(--s3); color: var(--text); }
.out-tab:hover { color: var(--text); }
.out-status { margin-left: auto; font-size: 12.5px; color: var(--muted); display: flex; align-items: center; gap: 8px; }
.out-status .ms { font-family: var(--mono); color: var(--faint); }
.out-body { flex: 1; overflow: auto; padding: 12px 18px 18px; }
.out-body pre { margin: 0; font-size: 13.5px; line-height: 1.65; white-space: pre-wrap; word-break: break-word; color: var(--soft); }
.out-body .empty { color: var(--faint); font-size: 13.5px; }
.out-body .err { color: #f3a5a5; }
.out-body .diff-line { display: flex; gap: 14px; }
.out-body .diff-line .ln { width: 22px; text-align: right; color: var(--faint); flex: none; user-select: none; }
.out-body .diff-line.bad { background: color-mix(in srgb, var(--bad) 10%, transparent); border-radius: 6px; }
.out-body .diff-line.bad .ln { color: var(--bad); }
.verdict { display: flex; align-items: center; gap: 12px; padding: 12px 14px; border-radius: 12px; margin-bottom: 12px; font-size: 14px; animation: rise 0.3s var(--ease); }
.verdict svg { width: 18px; height: 18px; flex: none; }
.verdict.pass { background: color-mix(in srgb, var(--good) 12%, var(--s1)); color: var(--text); }
.verdict.pass svg { color: var(--good); }
.verdict.fail { background: color-mix(in srgb, var(--bad) 10%, var(--s1)); color: var(--soft); }
.verdict.fail svg { color: var(--bad); }
.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.compare h5 { margin: 0 0 6px; font-size: 11.5px; font-weight: 500; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); }
.checks { display: flex; flex-direction: column; gap: 6px; }
.check-row { display: flex; align-items: center; gap: 10px; font-size: 14px; color: var(--soft); }
.check-row i { width: 18px; height: 18px; border-radius: 50%; display: grid; place-items: center; background: var(--s4); flex: none; }
.check-row i svg { width: 11px; height: 11px; }
.check-row.pass i { background: var(--good); color: #000; }
.check-row.fail i { background: color-mix(in srgb, var(--bad) 60%, var(--s4)); color: #000; }
.preview { width: 100%; height: 100%; border: 0; background: #fff; border-radius: 10px; }
.preview-wrap { flex: 1; padding: 0 12px 12px; display: flex; min-height: 0; }

.done-card { position: absolute; left: 50%; bottom: 22px; transform: translateX(-50%); z-index: 20; width: min(520px, calc(100% - 32px)); padding: 20px; border-radius: 22px; background: var(--s3); box-shadow: 0 30px 80px rgba(0, 0, 0, 0.7); animation: up 0.5s var(--ease); }
@keyframes up { from { opacity: 0; transform: translate(-50%, 20px); } to { opacity: 1; transform: translate(-50%, 0); } }
.done-card .top-line { display: flex; align-items: center; gap: 14px; }
.done-card .ring { width: 46px; height: 46px; border-radius: 50%; background: var(--lang); color: var(--lang-ink); display: grid; place-items: center; flex: none; }
.done-card .ring svg { width: 22px; height: 22px; }
.done-card h3 { font-size: 18px; }
.done-card .xp { margin-left: auto; font-family: var(--mono); font-size: 15px; color: var(--lang); }
.done-card .actions { display: flex; gap: 8px; margin-top: 16px; flex-wrap: wrap; }
.lesson-right { position: relative; }

.locked-page { max-width: 520px; margin: 12vh auto 0; text-align: center; padding: 0 24px; }
.locked-page .orb { width: 72px; height: 72px; margin: 0 auto 18px; border-radius: 50%; display: grid; place-items: center; background: var(--s3); color: var(--muted); }
.locked-page .orb svg { width: 28px; height: 28px; }
.locked-page h1 { font-size: 24px; }
.locked-page p { color: var(--muted); margin: 10px 0 22px; }

.lang-tabs { display: flex; gap: 6px; flex-wrap: wrap; }
.lang-tab { display: inline-flex; align-items: center; gap: 9px; height: 36px; padding: 0 14px; border-radius: 11px; background: var(--s2); color: var(--muted); font-size: 14px; font-weight: 500; transition: background 0.15s, color 0.15s; }
.lang-tab i { width: 8px; height: 8px; border-radius: 50%; background: var(--c); opacity: 0.5; }
.lang-tab:hover { color: var(--text); background: var(--s3); }
.lang-tab.on { background: color-mix(in srgb, var(--c) 16%, var(--s2)); color: var(--text); }
.lang-tab.on i { opacity: 1; }

.sandbox { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; height: calc(100vh - 60px - 150px); min-height: 460px; margin-top: 22px; }
.sandbox .pane { display: flex; flex-direction: column; border-radius: 22px; background: var(--s1); border: 1px solid var(--line); overflow: hidden; min-height: 0; }
.sandbox .pane .out-host { border-top: 0; flex: 1; }
.stdin { border-top: 1px solid var(--line); padding: 10px 14px 12px; flex: none; }
.stdin label { font-size: 12px; color: var(--muted); display: block; margin-bottom: 6px; }
.stdin textarea { width: 100%; height: 64px; resize: none; border: 0; border-radius: 10px; background: var(--s2); color: var(--text); font-family: var(--mono); font-size: 13px; padding: 8px 10px; }
.stdin textarea:focus { outline: none; background: var(--s3); }

.cheat-list { margin-top: 28px; display: flex; flex-direction: column; }
.cheat-sec { display: grid; grid-template-columns: 220px 1fr; gap: 24px; padding: 22px 0; border-top: 1px solid var(--line); }
.cheat-sec .h { font-weight: 600; }
.cheat-sec .h small { display: block; color: var(--muted); font-weight: 400; font-size: 13px; margin-top: 2px; }
.cheat-sec .items { display: flex; flex-direction: column; gap: 10px; }
.cheat-item .l { font-size: 13px; color: var(--muted); margin-bottom: 5px; }
.cheat-item .codeblock pre { padding: 10px 14px; font-size: 13px; }
.cheat-sec.locked { opacity: 0.42; }
.cheat-sec.locked .items { filter: blur(3px); pointer-events: none; user-select: none; }

.badges { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; margin-top: 24px; }
.badge { display: flex; align-items: center; gap: 14px; padding: 16px; border-radius: 18px; background: var(--s1); border: 1px solid var(--line); }
.badge .medal { width: 48px; height: 48px; border-radius: 15px; display: grid; place-items: center; flex: none; background: var(--s3); color: var(--faint); }
.badge .medal svg { width: 22px; height: 22px; }
.badge.got .medal { background: color-mix(in srgb, var(--c, #fff) 18%, var(--s2)); color: var(--c, #fff); box-shadow: 0 0 26px color-mix(in srgb, var(--c, #fff) 14%, transparent); }
.badge .t { font-weight: 500; font-size: 14.5px; }
.badge .d { font-size: 13px; color: var(--muted); }
.badge:not(.got) .t { color: var(--muted); }
.badge-mini { width: 40px; height: 40px; border-radius: 13px; display: grid; place-items: center; background: color-mix(in srgb, var(--c, #fff) 16%, var(--s2)); color: var(--c, #fff); }
.badge-mini svg { width: 18px; height: 18px; }

.toasts { position: fixed; right: 20px; bottom: 20px; z-index: 100; display: flex; flex-direction: column; gap: 8px; align-items: flex-end; }
.toast { display: flex; align-items: center; gap: 12px; padding: 12px 16px 12px 12px; border-radius: 14px; background: var(--s4); box-shadow: 0 16px 40px rgba(0, 0, 0, 0.6); font-size: 14px; animation: toast-in 0.4s var(--ease); max-width: 360px; }
.toast.out { animation: toast-out 0.3s var(--ease) forwards; }
.toast .ic { width: 32px; height: 32px; border-radius: 10px; display: grid; place-items: center; flex: none; background: color-mix(in srgb, var(--c, #fff) 18%, var(--s3)); color: var(--c, #fff); }
.toast .ic svg { width: 16px; height: 16px; }
.toast small { display: block; color: var(--muted); font-size: 12.5px; }
@keyframes toast-in { from { opacity: 0; transform: translateY(10px) scale(0.98); } to { opacity: 1; transform: none; } }
@keyframes toast-out { to { opacity: 0; transform: translateY(6px); } }

.cm-s-branch.CodeMirror { background: var(--s1); color: #d6d6db; font-family: var(--mono); font-size: 14px; line-height: 1.65; }
.cm-s-branch .CodeMirror-lines { padding: 14px 0; }
.cm-s-branch .CodeMirror-gutters { background: var(--s1); border: 0; }
.cm-s-branch .CodeMirror-linenumber { color: #3a3a41; padding: 0 14px 0 10px; }
.cm-s-branch .CodeMirror-activeline-background { background: rgba(255, 255, 255, 0.025); }
.cm-s-branch .CodeMirror-activeline-gutter .CodeMirror-linenumber { color: var(--muted); }
.cm-s-branch .CodeMirror-cursor { border-left: 2px solid var(--lang); }
.cm-s-branch .CodeMirror-selected, .cm-s-branch.CodeMirror-focused .CodeMirror-selected { background: rgba(255, 255, 255, 0.09); }
.cm-s-branch .CodeMirror-matchingbracket { color: var(--text) !important; background: rgba(255, 255, 255, 0.1); }
.cm-s-branch pre.CodeMirror-line, .cm-s-branch pre.CodeMirror-line-like { padding: 0 16px 0 6px; }
.cm-s-branch .cm-keyword, .cm-s-branch .cm-tag, .codeblock .cm-keyword, .codeblock .cm-tag { color: var(--lang); }
.cm-s-branch .cm-def, .codeblock .cm-def { color: #ffffff; }
.cm-s-branch .cm-string, .cm-s-branch .cm-string-2, .cm-s-branch .cm-number, .cm-s-branch .cm-atom,
.codeblock .cm-string, .codeblock .cm-string-2, .codeblock .cm-number, .codeblock .cm-atom { color: #a8d8a0; }
.cm-s-branch .cm-attribute, .cm-s-branch .cm-property, .codeblock .cm-attribute, .codeblock .cm-property { color: #c9c9d1; }
.cm-s-branch .cm-builtin, .cm-s-branch .cm-variable-3, .cm-s-branch .cm-type, .cm-s-branch .cm-qualifier,
.codeblock .cm-builtin, .codeblock .cm-variable-3, .codeblock .cm-type, .codeblock .cm-qualifier { color: #9db8ff; }
.cm-s-branch .cm-comment, .codeblock .cm-comment { color: #55555d; font-style: italic; }
.cm-s-branch .cm-operator, .cm-s-branch .cm-bracket, .codeblock .cm-operator, .codeblock .cm-bracket { color: #8b8b93; }
.cm-s-branch .cm-meta, .codeblock .cm-meta { color: #8b8b93; }

@media (max-width: 1000px) {
  .lesson { grid-template-columns: 1fr; height: auto; }
  .lesson-left { border-right: 0; overflow: visible; }
  .lesson-right { height: 80vh; position: sticky; bottom: 0; }
  .course-head { grid-template-columns: 1fr; }
  .side { position: static; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .sandbox { grid-template-columns: 1fr; height: auto; }
  .sandbox .pane { height: 420px; }
  .cheat-sec { grid-template-columns: 1fr; gap: 10px; }
}
@media (max-width: 680px) {
  .top { gap: 12px; padding: 0 16px; }
  .brand-name, .top-stats .level-chip .bar { display: none; }
  .nav a { padding: 6px 9px; font-size: 13px; }
  .page { padding: 28px 16px 60px; }
  .hero { flex-direction: column; align-items: flex-start; }
  .lesson-inner { padding: 24px 16px 100px; }
}