:root{
  --bg:#f4f5f7; --card:#ffffff; --ink:#1c1f23; --muted:#6b7280; --line:#e5e7eb;
  --accent:#2f5d62; --accent-ink:#ffffff; --accent-soft:#eef3f3;
  --code-bg:#1a2426; --code-ink:#dbe7e8; --code-num:#6f8b8e;
  --shadow:0 1px 2px rgba(16,24,40,.04),0 12px 32px rgba(16,24,40,.08);
  --radius:16px;
}
@media (prefers-color-scheme: dark){
  :root{
    --bg:#111315; --card:#191c1f; --ink:#e9ecef; --muted:#9aa4af; --line:#2a2f34;
    --accent:#8fc0c4; --accent-ink:#0d1113; --accent-soft:#1e2528;
    --code-bg:#0d1113; --code-ink:#cfe0e2; --code-num:#5b7477;
    --shadow:0 1px 2px rgba(0,0,0,.3),0 12px 32px rgba(0,0,0,.35);
  }
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg); color:var(--ink);
  font:400 16px/1.62 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}

/* ---------- шапка / подвал ---------- */
.top{
  max-width:960px;margin:0 auto;padding:22px 20px 8px;
}
.brand{display:inline-flex;align-items:center;gap:12px;color:var(--ink);font-weight:650}
.brand:hover{text-decoration:none}
.brand-mark{
  display:inline-grid;place-items:center;width:38px;height:38px;border-radius:12px;
  background:var(--accent-soft);color:var(--accent);font:700 15px/1 ui-monospace,SFMono-Regular,Menlo,monospace
}
.brand small{display:block;font-weight:400;font-size:12.5px;color:var(--muted);margin-top:2px}
main{max-width:960px;margin:0 auto;padding:8px 20px 56px}
.bottom{
  max-width:960px;margin:0 auto;padding:20px;border-top:1px solid var(--line);
  display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap;color:var(--muted);font-size:13px
}

/* ---------- главная ---------- */
.hero{padding:14px 0 6px}
h1{font-size:30px;line-height:1.2;margin:0 0 10px;letter-spacing:-.015em;font-weight:700}
.lead{color:var(--muted);font-size:16.5px;margin:0 0 10px;max-width:64ch}
.muted{color:var(--muted)}
.small{font-size:13.5px}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:16px;margin-top:24px}
.card{
  display:block;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:20px;box-shadow:var(--shadow);color:var(--ink);transition:transform .08s ease,border-color .15s ease
}
.card:hover{border-color:var(--accent);transform:translateY(-1px);text-decoration:none}
.card-top{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-bottom:12px}
.num{
  display:inline-grid;place-items:center;min-width:34px;height:28px;padding:0 8px;border-radius:8px;
  background:var(--accent-soft);color:var(--accent);font:700 13px/1 ui-monospace,SFMono-Regular,Menlo,monospace
}
.level{font-size:12px;text-transform:uppercase;letter-spacing:.06em;color:var(--muted)}
.card h2{font-size:19px;margin:0 0 8px;font-weight:650}
.card p{margin:0 0 14px;color:var(--muted);font-size:14.5px}
.more{font-size:14px;color:var(--accent);font-weight:600}

/* ---------- страница задания ---------- */
.task{max-width:820px}
.eyebrow{font-size:13px;color:var(--muted);margin:6px 0 12px}
.task h1{display:flex;align-items:baseline;gap:12px;font-size:28px}
.hnum{
  font:700 14px/1 ui-monospace,SFMono-Regular,Menlo,monospace;color:var(--accent);
  background:var(--accent-soft);border-radius:8px;padding:6px 9px
}
.meta{margin:6px 0 8px}
.block{margin-top:34px}
.block h2{font-size:18px;margin:0 0 12px;font-weight:650}
.steps{margin:0;padding-left:22px}
.steps li{margin:0 0 8px}
.chips{display:flex;flex-wrap:wrap;gap:8px;list-style:none;margin:0;padding:0}
.chips li{
  border:1px solid var(--line);background:var(--card);border-radius:999px;
  padding:7px 13px;font-size:14px
}
.scheme-box{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:14px;box-shadow:var(--shadow);overflow:hidden
}
.scheme-box img{display:block;width:100%;height:auto;border-radius:10px}

/* ---------- код (без возможности копирования) ---------- */
.code{
  background:var(--code-bg);color:var(--code-ink);border-radius:14px;padding:16px 0;
  font:400 14px/1.65 ui-monospace,SFMono-Regular,Menlo,Consolas,"Liberation Mono",monospace;
  overflow-x:auto;box-shadow:var(--shadow);
  -webkit-user-select:none;user-select:none;-webkit-touch-callout:none;cursor:default
}
.code .cline{display:flex;min-width:max-content}
.code .cline:hover{background:rgba(255,255,255,.04)}
.code .cnum{
  flex:0 0 46px;text-align:right;padding-right:14px;color:var(--code-num);
  -webkit-user-select:none;user-select:none
}
.code .csrc{white-space:pre;padding-right:18px}

/* ---------- пояснения ---------- */
.explain{width:100%;border-collapse:collapse;font-size:14.5px;background:var(--card);
  border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.explain th,.explain td{text-align:left;padding:11px 14px;border-bottom:1px solid var(--line);vertical-align:top}
.explain thead th{background:var(--accent-soft);color:var(--ink);font-size:13px;
  text-transform:uppercase;letter-spacing:.05em}
.explain tbody tr:last-child td{border-bottom:0}
.explain .rows-num{
  width:92px;white-space:nowrap;font:700 13px/1.5 ui-monospace,SFMono-Regular,Menlo,monospace;color:var(--accent)
}

/* ---------- навигация ---------- */
.pager{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;margin-top:38px}
.btn{
  display:inline-block;border-radius:12px;padding:11px 16px;font-size:14.5px;font-weight:600;
  background:var(--accent);color:var(--accent-ink);border:0;cursor:pointer
}
.btn:hover{opacity:.92;text-decoration:none}
.btn.ghost{background:transparent;color:var(--accent);border:1px solid var(--line)}
.btn.ghost:hover{border-color:var(--accent)}

@media (max-width:560px){
  h1{font-size:24px}
  .task h1{font-size:22px;flex-wrap:wrap}
  main{padding:8px 14px 44px}
  .top,.bottom{padding-left:14px;padding-right:14px}
  .code{font-size:12.5px}
  .explain .rows-num{width:64px}
}