:root {
  --blue: #2f6ea5; --blue-dark: #1f4e79; --blue-soft: #e8f0f8;
  --yellow: #ffd43b; --yellow-soft: #fff6d1;
  --ink: #1d2733; --muted: #5d6b7a; --line: #dde3ea; --bg: #f5f7fa; --card: #ffffff;
  --green: #1e8a4c; --green-soft: #e3f4ea; --red: #c0392b; --red-soft: #fbe9e7; --amber: #9a6700; --amber-soft: #fff4d6;
  --mono: ui-monospace, "Cascadia Code", Consolas, "DejaVu Sans Mono", monospace;
  --radius: 10px;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body { font: 15px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif; color: var(--ink); background: var(--bg); }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre, .mono { font-family: var(--mono); font-size: 0.92em; }
code { background: var(--blue-soft); padding: 1px 5px; border-radius: 4px; }
h1 { font-size: 1.6rem; margin: 0 0 4px; }
h2 { font-size: 1.2rem; margin: 26px 0 10px; }
h3 { font-size: 1.02rem; margin: 0 0 6px; }
.muted { color: var(--muted); }
.small { font-size: 0.86rem; }

/* header */
.top { background: var(--blue-dark); color: #fff; }
.top .wrap { display: flex; align-items: center; gap: 18px; min-height: 56px; flex-wrap: wrap; }
.brand { color: #fff; font-weight: 700; font-size: 1.1rem; display: flex; align-items: center; gap: 8px; }
.brand:hover { text-decoration: none; }
.logo { width: 26px; height: 26px; border-radius: 6px; background: var(--yellow); color: var(--blue-dark);
        display: grid; place-items: center; font-family: var(--mono); font-weight: 800; font-size: 13px; }
.top nav { display: flex; gap: 4px; flex-wrap: wrap; margin-left: auto; align-items: center; }
.top nav a, .top nav button { color: #dce8f4; padding: 6px 10px; border-radius: 6px; font: inherit; background: none; border: 0; cursor: pointer; }
.top nav a:hover, .top nav button:hover, .top nav a.on { background: rgba(255,255,255,.12); color: #fff; text-decoration: none; }
.who { color: #b9cde1; font-size: .86rem; padding: 0 6px; }

.wrap { max-width: 1180px; margin: 0 auto; padding: 0 20px; }
main.wrap { padding-top: 26px; padding-bottom: 60px; }
.wide main.wrap { max-width: 1500px; }

/* cards & grids */
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; }
.grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.daycard { display: flex; flex-direction: column; gap: 10px; color: inherit; position: relative; }
.daycard:hover { border-color: var(--blue); text-decoration: none; box-shadow: 0 2px 10px rgba(31,78,121,.08); }
.daycard.locked { opacity: .55; pointer-events: none; }
.daynum { font-family: var(--mono); font-size: .8rem; color: var(--blue); font-weight: 700; letter-spacing: .04em; text-transform: uppercase; }
.daycard h3 { font-size: 1.08rem; }
.stats { display: flex; gap: 14px; font-size: .88rem; color: var(--muted); margin-top: auto; }
.stats b { color: var(--ink); }
.bar { height: 6px; background: #edf1f5; border-radius: 4px; overflow: hidden; }
.bar i { display: block; height: 100%; background: var(--green); }

.badge { display: inline-block; font-size: .74rem; font-weight: 600; padding: 2px 8px; border-radius: 99px; background: #eef1f4; color: var(--muted); white-space: nowrap; }
.badge.open { background: var(--green-soft); color: var(--green); }
.badge.closed { background: var(--amber-soft); color: var(--amber); }
.badge.locked { background: #eef1f4; color: var(--muted); }
.badge.ok { background: var(--green-soft); color: var(--green); }
.badge.bad { background: var(--red-soft); color: var(--red); }
.badge.part { background: var(--yellow-soft); color: var(--amber); }
.daycard .badge { position: absolute; top: 16px; right: 16px; }

/* buttons & forms */
.btn { display: inline-flex; align-items: center; gap: 6px; padding: 8px 16px; border-radius: 8px; border: 1px solid var(--blue);
       background: var(--blue); color: #fff; font: inherit; font-weight: 600; cursor: pointer; text-decoration: none; }
.btn:hover { background: var(--blue-dark); text-decoration: none; }
.btn.ghost { background: #fff; color: var(--blue); }
.btn.ghost:hover { background: var(--blue-soft); }
.btn.go { background: var(--green); border-color: var(--green); }
.btn.go:hover { background: #166b3a; }
.btn.danger { background: #fff; color: var(--red); border-color: #e6b8b2; }
.btn.small { padding: 4px 10px; font-size: .85rem; font-weight: 500; }
.btn[disabled] { opacity: .55; cursor: wait; }
label { display: block; font-weight: 600; margin: 12px 0 4px; font-size: .92rem; }
input[type=text], input[type=password], textarea, select {
  width: 100%; padding: 9px 11px; border: 1px solid #c8d1db; border-radius: 8px; font: inherit; background: #fff; color: var(--ink); }
textarea { font-family: var(--mono); font-size: .9rem; }
input:focus, textarea:focus, select:focus { outline: 2px solid #9cc0e3; border-color: var(--blue); }
.formcard { max-width: 420px; margin: 40px auto; }
.formcard .btn { width: 100%; justify-content: center; margin-top: 18px; }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.spacer { flex: 1; }

/* flash */
.flash { padding: 10px 14px; border-radius: 8px; margin-bottom: 16px; border: 1px solid; }
.flash.ok { background: var(--green-soft); border-color: #b9e1c8; color: #14572f; }
.flash.error { background: var(--red-soft); border-color: #f0c3bd; color: #8e2a1f; }
code.pw { font-size: 1.05rem; background: #fff; border: 1px solid var(--line); }

/* tables */
table { width: 100%; border-collapse: collapse; background: #fff; }
th, td { text-align: left; padding: 9px 10px; border-bottom: 1px solid var(--line); vertical-align: middle; }
th { font-size: .8rem; text-transform: uppercase; letter-spacing: .03em; color: var(--muted); background: #fafbfc; }
.tablewrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--radius); }
.tablewrap table { border: 0; }
td.num, th.num { text-align: center; }
.results td { white-space: nowrap; font-size: .9rem; }
.results .cell { display: inline-block; min-width: 72px; }
.seg { display: inline-flex; border: 1px solid #c8d1db; border-radius: 8px; overflow: hidden; }
.seg button { border: 0; background: #fff; padding: 5px 12px; font: inherit; font-size: .86rem; cursor: pointer; color: var(--muted); }
.seg button + button { border-left: 1px solid #c8d1db; }
.seg button.on.open { background: var(--green); color: #fff; }
.seg button.on.closed { background: var(--amber); color: #fff; }
.seg button.on.locked { background: #6b7785; color: #fff; }

/* unit page */
.topics { margin: 8px 0 0; padding-left: 20px; columns: 2; column-gap: 32px; }
.topics li { margin-bottom: 4px; break-inside: avoid; }
.plist { display: flex; flex-direction: column; gap: 10px; }
.pitem { display: flex; align-items: center; gap: 12px; padding: 12px 16px; color: inherit; }
.pitem:hover { border-color: var(--blue); text-decoration: none; }
.pnum { width: 30px; height: 30px; border-radius: 50%; display: grid; place-items: center; background: var(--blue-soft); color: var(--blue); font-weight: 700; font-family: var(--mono); flex: none; }
.pitem.done .pnum { background: var(--green); color: #fff; }

/* quiz */
.quizbar { position: sticky; top: 0; z-index: 5; background: var(--bg); padding: 10px 0; display: flex; align-items: center; gap: 12px; border-bottom: 1px solid var(--line); margin-bottom: 18px; }
.timer { font-family: var(--mono); font-weight: 700; font-size: 1.15rem; padding: 4px 12px; border-radius: 8px; background: var(--blue-soft); color: var(--blue-dark); }
.timer.low { background: var(--red-soft); color: var(--red); }
.q { margin-bottom: 14px; }
.q .qtext { font-weight: 600; margin-bottom: 8px; }
.q pre.code { background: #1e2a36; color: #e6edf3; padding: 12px 14px; border-radius: 8px; overflow-x: auto; margin: 0 0 10px; line-height: 1.45; }
.opts { display: flex; flex-direction: column; gap: 6px; }
.opt { display: flex; gap: 10px; align-items: flex-start; padding: 8px 12px; border: 1px solid var(--line); border-radius: 8px; cursor: pointer; font-weight: 400; margin: 0; }
.opt:hover { background: #f8fafc; }
.opt input { margin-top: 4px; }
.opt span { white-space: pre-wrap; }
.opts.mono .opt span { font-family: var(--mono); font-size: .9rem; }
.opt.correct { border-color: #9fd3b4; background: var(--green-soft); }
.opt.wrong { border-color: #f0b7ae; background: var(--red-soft); }
.opt .tag { margin-left: auto; font-family: inherit; font-size: .78rem; font-weight: 600; white-space: nowrap; }
.explain { margin-top: 8px; font-size: .9rem; color: var(--muted); }
.qnum { color: var(--blue); font-family: var(--mono); margin-right: 6px; }
.scorebig { font-size: 2.4rem; font-weight: 800; color: var(--blue-dark); line-height: 1; }

/* problem / editor */
.split { display: grid; grid-template-columns: minmax(300px, 0.9fr) 1.1fr; gap: 18px; align-items: start; }
.statement p { margin: 0 0 10px; }
.statement ul, .statement ol { margin: 0 0 10px; padding-left: 22px; }
pre.sample { background: #f3f6f9; border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; margin: 0 0 10px; overflow-x: auto; white-space: pre; }
.samplebox { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.samplebox h4 { margin: 0 0 4px; font-size: .78rem; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
.editorcard { padding: 0; overflow: hidden; }
.edhead { display: flex; align-items: center; gap: 8px; padding: 8px 12px; border-bottom: 1px solid var(--line); background: #fafbfc; flex-wrap: wrap; }
.edhead .file { font-family: var(--mono); font-size: .85rem; color: var(--muted); }
.CodeMirror { height: 420px; font-family: var(--mono); font-size: 14px; line-height: 1.5; }
.CodeMirror-gutters { background: #f6f8fa; border-right: 1px solid var(--line); }
textarea.fallback { height: 420px; border: 0; border-radius: 0; tab-size: 4; }
.io { display: grid; grid-template-columns: 1fr 1.4fr; border-top: 1px solid var(--line); }
.io > div { padding: 10px 12px; }
.io > div + div { border-left: 1px solid var(--line); }
.io h4 { margin: 0 0 6px; font-size: .78rem; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
.io textarea { height: 110px; resize: vertical; }
.out { background: #1e2a36; color: #e6edf3; font-family: var(--mono); font-size: .86rem; min-height: 110px; max-height: 260px; overflow: auto; padding: 8px 10px; border-radius: 8px; white-space: pre-wrap; margin: 0; }
.out .err { color: #ff9b8f; }
.out .dim { color: #8aa0b4; }
.edfoot { display: flex; gap: 8px; align-items: center; padding: 10px 12px; border-top: 1px solid var(--line); flex-wrap: wrap; }
.tests { margin-top: 14px; }
.verdict { display: flex; align-items: center; gap: 12px; padding: 12px 16px; border-radius: 10px; margin-bottom: 10px; font-weight: 600; }
.verdict.ok { background: var(--green-soft); color: #14572f; }
.verdict.part { background: var(--yellow-soft); color: #6b4a00; }
.verdict.bad { background: var(--red-soft); color: #8e2a1f; }
.test { border: 1px solid var(--line); border-radius: 8px; margin-bottom: 8px; background: #fff; }
.test summary { padding: 8px 12px; cursor: pointer; display: flex; gap: 10px; align-items: center; }
.test .body { padding: 0 12px 12px; display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
.test .body pre { background: #f3f6f9; border: 1px solid var(--line); border-radius: 6px; padding: 6px 8px; margin: 0; white-space: pre-wrap; font-size: .82rem; max-height: 180px; overflow: auto; }
.test .body .wide { grid-column: 1 / -1; }
.test .body h5 { margin: 0 0 3px; font-size: .74rem; color: var(--muted); text-transform: uppercase; }
.solution pre { background: #1e2a36; color: #e6edf3; padding: 12px; border-radius: 8px; overflow-x: auto; }
.crumbs { font-size: .88rem; margin-bottom: 6px; color: var(--muted); }
.crumbs a { color: var(--muted); }
.note { background: var(--yellow-soft); border: 1px solid #f1df9c; border-radius: 8px; padding: 10px 14px; font-size: .9rem; }

@media (max-width: 900px) {
  .split { grid-template-columns: 1fr; }
  .topics { columns: 1; }
  .io { grid-template-columns: 1fr; }
  .io > div + div { border-left: 0; border-top: 1px solid var(--line); }
  .test .body { grid-template-columns: 1fr; }
}
@media (max-width: 560px) {
  .wrap { padding: 0 14px; }
  .samplebox { grid-template-columns: 1fr; }
  .CodeMirror, textarea.fallback { height: 320px; }
}
@media print {
  .top, .noprint, .flash { display: none !important; }
  body { background: #fff; }
}