:root {
  --bg: #0d1117; --panel: #151b24; --panel2: #1c2430; --line: #263041;
  --text: #e6edf3; --muted: #8b98a9; --accent: #3ddc84; --accent-ink: #062b16;
  --bad: #ff6b6b; --warn: #f5b942; --mid: #5aa9ff;
  --mono: ui-monospace, "JetBrains Mono", "Fira Code", Menlo, monospace;
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text);
  font: 16px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre { font-family: var(--mono); }
code { background: var(--panel2); padding: 1px 6px; border-radius: 5px; font-size: .9em; word-break: break-word; }
pre { background: #0a0e14; border: 1px solid var(--line); padding: 14px 16px; border-radius: 8px;
  overflow-x: auto; white-space: pre-wrap; word-break: break-all; color: #b8f5cf; }
h1, h2, h3 { line-height: 1.25; }
.muted { color: var(--muted); }
.small { font-size: 14px; }

.top { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap;
  padding: 14px 24px; border-bottom: 1px solid var(--line); background: rgba(13,17,23,.9);
  position: sticky; top: 0; backdrop-filter: blur(6px); z-index: 5; }
.logo { font-weight: 800; font-size: 20px; color: var(--text); letter-spacing: .3px; }
.logo span { filter: drop-shadow(0 0 6px rgba(61,220,132,.6)); }
nav { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; }
nav a { color: var(--muted); font-weight: 500; }
nav a:hover { color: var(--text); text-decoration: none; }
.me { color: var(--text); font-weight: 600; }
.inline { display: inline; margin: 0; }
button.link { background: none; border: 0; color: var(--muted); font: inherit; cursor: pointer; padding: 0; }
button.link:hover { color: var(--bad); }

main { max-width: 1040px; margin: 0 auto; padding: 28px 16px 60px; }
footer { text-align: center; color: var(--muted); font-size: 13px; padding: 24px; border-top: 1px solid var(--line); }

.btn { display: inline-block; background: var(--accent); color: var(--accent-ink); font-weight: 700;
  border: 0; border-radius: 8px; padding: 10px 18px; cursor: pointer; font-size: 15px; }
.btn:hover { filter: brightness(1.1); text-decoration: none; }
.btn.small { padding: 6px 12px; font-size: 14px; color: var(--accent-ink); }
.btn.ghost { background: transparent; color: var(--accent); border: 1px solid var(--accent); }

.flash { background: var(--panel2); border-left: 4px solid var(--accent); padding: 10px 14px; border-radius: 6px; margin-bottom: 18px; }

.hero { display: grid; grid-template-columns: 1fr 260px; gap: 24px; align-items: center; margin-bottom: 18px; }
.hero h1 { font-size: 32px; margin: 0 0 8px; }
.hero p { color: var(--muted); margin: 0; }
.progress-card { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 18px; }
.progress-card p { color: var(--muted); margin: 0 0 12px; }
.big { font-size: 30px; font-weight: 800; }
.big small { font-size: 15px; color: var(--muted); font-weight: 500; }
.bar { height: 8px; background: var(--panel2); border-radius: 99px; overflow: hidden; margin: 10px 0 6px; }
.bar div { height: 100%; background: linear-gradient(90deg, var(--accent), #a6f4c5); border-radius: 99px; }

h2.cat { font-size: 15px; text-transform: uppercase; letter-spacing: 1.5px; color: var(--muted);
  margin: 34px 0 12px; border-bottom: 1px solid var(--line); padding-bottom: 6px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; }
.card { display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px;
  color: var(--text); transition: transform .12s, border-color .12s; }
.card:hover { transform: translateY(-2px); border-color: var(--accent); text-decoration: none; }
.card.done { border-color: rgba(61,220,132,.45); background: linear-gradient(180deg, rgba(61,220,132,.08), var(--panel)); }
.card-top { display: flex; justify-content: space-between; align-items: center; }
.pts { font-family: var(--mono); color: var(--accent); font-weight: 700; font-size: 14px; }
.check { color: var(--accent); font-size: 13px; }
.card .name { font-size: 18px; font-weight: 700; margin: 6px 0 8px; }
.meta { display: flex; justify-content: space-between; font-size: 13px; }
.diff { padding: 1px 8px; border-radius: 99px; background: var(--panel2); }
.d-10, .d-50, .d-75 { color: var(--accent); }
.d-100 { color: var(--mid); }
.d-150 { color: var(--warn); }

.back { color: var(--muted); font-size: 14px; }
.chal { background: var(--panel); border: 1px solid var(--line); border-radius: 14px; padding: 24px 28px; margin-top: 12px; }
.chal-head { display: flex; justify-content: space-between; align-items: flex-start; gap: 12px; }
.chal h1 { margin: 2px 0 8px; font-size: 30px; }
.tag { color: var(--muted); font-size: 14px; text-transform: uppercase; letter-spacing: 1px; }
.pts.big { font-size: 22px; }
.desc { font-size: 17px; }
.files { display: flex; gap: 10px; flex-wrap: wrap; margin: 16px 0; }
.chal h3 { margin: 26px 0 6px; }
.hint { background: var(--panel2); border: 1px solid var(--line); border-radius: 8px; margin: 8px 0; }
.hint summary { cursor: pointer; padding: 10px 14px; font-weight: 600; color: var(--warn); }
.hint div { padding: 0 14px 12px; }
.writeup { background: rgba(61,220,132,.06); border: 1px solid rgba(61,220,132,.3); border-radius: 8px; padding: 4px 16px; }
.result { margin: 22px 0 10px; padding: 12px 16px; border-radius: 8px; font-weight: 600; }
.result.ok { background: rgba(61,220,132,.12); color: var(--accent); border: 1px solid rgba(61,220,132,.4); }
.result.bad { background: rgba(255,107,107,.1); color: var(--bad); border: 1px solid rgba(255,107,107,.35); }
.submit { display: flex; gap: 10px; margin-top: 22px; }
.submit input { flex: 1; min-width: 0; }
input { background: #0a0e14; border: 1px solid var(--line); color: var(--text); border-radius: 8px;
  padding: 10px 12px; font: 15px var(--mono); }
input:focus { outline: 2px solid var(--accent); border-color: transparent; }
.stats { margin-top: 18px; }

.auth { max-width: 380px; margin: 30px auto; background: var(--panel); border: 1px solid var(--line); border-radius: 14px; padding: 24px; }
.auth h1 { margin-top: 0; }
.auth label { display: block; margin-bottom: 14px; font-weight: 600; }
.auth input { display: block; width: 100%; margin-top: 6px; font-family: inherit; }
.auth .btn { width: 100%; }

.board { width: 100%; border-collapse: collapse; background: var(--panel); border-radius: 12px; overflow: hidden; }
.board th, .board td { padding: 12px 16px; text-align: left; border-bottom: 1px solid var(--line); }
.board th { color: var(--muted); font-size: 13px; text-transform: uppercase; letter-spacing: 1px; background: var(--panel2); }
.me-row { background: rgba(61,220,132,.08); }

.guide h2 { margin-top: 32px; }
.tools { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 14px; }
.tools > div { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 4px 16px; }
.tools h3 { margin-bottom: 4px; }

@media (max-width: 700px) {
  .hero { grid-template-columns: 1fr; }
  .top { padding: 12px 16px; }
  nav { gap: 12px; font-size: 15px; }
  .chal { padding: 18px 16px; }
  .chal h1 { font-size: 24px; }
  .submit { flex-direction: column; }
  .board th, .board td { padding: 10px; }
}