/* DSA Mastery Plan — tracker styles. No build step, no dependencies. */
:root {
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-2: #f0f2f8;
  --border: #e3e6ef;
  --text: #16181d;
  --muted: #5f6675;
  --accent: #2563eb;
  --accent-contrast: #ffffff;
  --easy: #16a34a;
  --medium: #d97706;
  --hard: #dc2626;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.06), 0 1px 3px rgba(16, 24, 40, 0.08);
  --radius: 12px;
  --font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light;
}
:root[data-theme="dark"] {
  --bg: #0f1117;
  --surface: #171a23;
  --surface-2: #1f2330;
  --border: #2a2f3d;
  --text: #e8eaf0;
  --muted: #9aa3b5;
  --accent: #60a5fa;
  --accent-contrast: #0b1020;
  --easy: #4ade80;
  --medium: #fbbf24;
  --hard: #f87171;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
button, input, select, textarea { font: inherit; color: inherit; }
button { cursor: pointer; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.skip-link { position: absolute; left: -999px; top: 8px; background: var(--accent); color: var(--accent-contrast); padding: 8px 12px; border-radius: 8px; z-index: 100; }
.skip-link:focus { left: 8px; }

/* ---------- layout ---------- */
.topbar {
  position: sticky; top: 0; z-index: 20;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  max-width: 1120px; margin: 0 auto; padding: 10px 20px;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: -0.01em; color: var(--text); }
.brand svg { width: 28px; height: 28px; }
.brand small { font-weight: 500; color: var(--muted); }
.nav { display: flex; gap: 4px; margin-left: auto; flex-wrap: wrap; }
.nav a {
  padding: 6px 12px; border-radius: 999px; color: var(--muted); font-weight: 500; font-size: 14px;
}
.nav a:hover { background: var(--surface-2); text-decoration: none; color: var(--text); }
.nav a.active { background: var(--accent); color: var(--accent-contrast); }
.search {
  display: flex; align-items: center; gap: 6px;
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 999px; padding: 4px 10px;
}
.search input { border: 0; background: transparent; width: 180px; outline: none; }
.search kbd { font-family: var(--mono); font-size: 11px; color: var(--muted); border: 1px solid var(--border); border-radius: 4px; padding: 0 5px; }
.icon-btn {
  border: 1px solid var(--border); background: var(--surface); border-radius: 999px; width: 36px; height: 36px;
  display: inline-grid; place-items: center; color: var(--muted);
}
.icon-btn:hover { color: var(--text); background: var(--surface-2); }
main { max-width: 1120px; margin: 0 auto; padding: 24px 20px 80px; }
footer { max-width: 1120px; margin: 0 auto; padding: 0 20px 40px; color: var(--muted); font-size: 13px; }

/* ---------- components ---------- */
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 18px 20px;
}
.grid { display: grid; gap: 14px; }
.grid.cols-2 { grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.grid.cols-3 { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.grid.cols-4 { grid-template-columns: repeat(auto-fit, minmax(170px, 1fr)); }
.row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.between { justify-content: space-between; }
.muted { color: var(--muted); }
.small { font-size: 13px; }
.tiny { font-size: 12px; }
.mt { margin-top: 16px; }
.mb { margin-bottom: 16px; }
h1, h2, h3 { letter-spacing: -0.015em; line-height: 1.25; margin: 0 0 8px; }
h1 { font-size: 28px; }
h2 { font-size: 20px; }
h3 { font-size: 16px; }
.eyebrow { text-transform: uppercase; letter-spacing: 0.08em; font-size: 11px; font-weight: 700; color: var(--muted); }
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 8px 14px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface); font-weight: 600; font-size: 14px; color: var(--text);
}
.btn:hover { background: var(--surface-2); text-decoration: none; }
.btn.primary { background: var(--accent); color: var(--accent-contrast); border-color: transparent; }
.btn.primary:hover { filter: brightness(1.05); }
.btn.danger { color: var(--hard); }
.btn.sm { padding: 5px 10px; font-size: 13px; }
.chip {
  display: inline-flex; align-items: center; gap: 4px; padding: 2px 8px; border-radius: 999px;
  font-size: 12px; font-weight: 600; border: 1px solid var(--border); background: var(--surface-2); color: var(--muted);
  white-space: nowrap;
}
.chip.easy { color: var(--easy); border-color: color-mix(in srgb, var(--easy) 35%, transparent); background: color-mix(in srgb, var(--easy) 10%, transparent); }
.chip.medium { color: var(--medium); border-color: color-mix(in srgb, var(--medium) 35%, transparent); background: color-mix(in srgb, var(--medium) 10%, transparent); }
.chip.hard { color: var(--hard); border-color: color-mix(in srgb, var(--hard) 35%, transparent); background: color-mix(in srgb, var(--hard) 10%, transparent); }
.chip.core { color: #b45309; border-color: #f5d28a; background: #fff7e0; }
:root[data-theme="dark"] .chip.core { color: #fbbf24; border-color: #5b4712; background: #2a2210; }
.chip.kind-learn { color: var(--accent); }
.chip.kind-review { color: #7c3aed; }
.chip.kind-mock { color: var(--hard); }
.chip.phase { color: #fff; border-color: transparent; }

.progress { height: 8px; background: var(--surface-2); border-radius: 999px; overflow: hidden; border: 1px solid var(--border); }
.progress > span { display: block; height: 100%; background: var(--accent); border-radius: 999px; transition: width .3s ease; }
.ring { position: relative; width: 64px; height: 64px; }
.ring svg { transform: rotate(-90deg); }
.ring circle { fill: none; stroke-width: 7; }
.ring .track { stroke: var(--surface-2); }
.ring .bar { stroke: var(--accent); stroke-linecap: round; transition: stroke-dashoffset .4s ease; }
.ring .label { position: absolute; inset: 0; display: grid; place-items: center; font-size: 13px; font-weight: 700; }

/* checkbox rows */
.problem-row {
  display: grid; grid-template-columns: 24px 1fr auto; gap: 10px; align-items: center;
  padding: 9px 6px; border-top: 1px solid var(--border);
}
.problem-row:first-child { border-top: 0; }
.problem-row input[type="checkbox"] { width: 18px; height: 18px; accent-color: var(--accent); margin: 0; }
.problem-row .title { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; min-width: 0; }
.problem-row .title a { color: var(--text); font-weight: 500; }
.problem-row.done .title a { color: var(--muted); text-decoration: line-through; }
.problem-row .num { font-family: var(--mono); font-size: 12px; color: var(--muted); }
.problem-row .meta { display: flex; gap: 6px; align-items: center; }
.vid { display: inline-grid; place-items: center; width: 22px; height: 22px; border-radius: 6px; background: var(--surface-2); border: 1px solid var(--border); color: var(--muted); font-size: 11px; }
.vid:hover { color: var(--hard); text-decoration: none; }

/* day list */
.day-row {
  display: grid; grid-template-columns: 54px 1fr auto; gap: 12px; align-items: center;
  padding: 10px 12px; border-radius: 10px; border: 1px solid transparent; color: var(--text);
}
.day-row:hover { background: var(--surface-2); text-decoration: none; }
.day-row.today { border-color: var(--accent); }
.day-row .daynum { font-family: var(--mono); font-weight: 700; color: var(--muted); }
.day-row .topic { font-weight: 600; }
.day-row .sub { color: var(--muted); font-size: 13px; }
.day-row .dots { display: flex; gap: 3px; }
.dot { width: 10px; height: 10px; border-radius: 3px; background: var(--surface-2); border: 1px solid var(--border); }
.dot.on { background: var(--accent); border-color: var(--accent); }
.dot.easy.on { background: var(--easy); border-color: var(--easy); }
.dot.medium.on { background: var(--medium); border-color: var(--medium); }
.dot.hard.on { background: var(--hard); border-color: var(--hard); }

/* tables */
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { text-align: left; padding: 9px 10px; border-bottom: 1px solid var(--border); vertical-align: middle; }
th { font-size: 12px; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 700; position: sticky; top: 58px; background: var(--surface); }
tr:hover td { background: var(--surface-2); }
td.num { font-family: var(--mono); color: var(--muted); font-size: 12px; }

/* heatmap */
.heatmap { display: grid; grid-auto-flow: column; grid-template-rows: repeat(7, 12px); gap: 3px; overflow-x: auto; padding-bottom: 6px; }
.heatmap i { width: 12px; height: 12px; border-radius: 3px; background: var(--surface-2); border: 1px solid var(--border); display: block; }
.heatmap i.l1 { background: color-mix(in srgb, var(--accent) 30%, var(--surface-2)); }
.heatmap i.l2 { background: color-mix(in srgb, var(--accent) 55%, var(--surface-2)); }
.heatmap i.l3 { background: color-mix(in srgb, var(--accent) 80%, var(--surface-2)); }
.heatmap i.l4 { background: var(--accent); }

/* hero */
.hero { display: grid; grid-template-columns: 1.4fr 1fr; gap: 20px; align-items: stretch; }
@media (max-width: 800px) { .hero { grid-template-columns: 1fr; } .search input { width: 120px; } }
.stat { display: flex; flex-direction: column; gap: 2px; }
.stat b { font-size: 24px; letter-spacing: -0.02em; }
.stat span { color: var(--muted); font-size: 12px; }
.phase-card { border-left: 4px solid var(--accent); }
.phase-card > .row.between { flex-wrap: nowrap; align-items: flex-start; }
.phase-card .ring { flex-shrink: 0; }
.grid.top { align-items: start; }
.phase-card h3 a { color: var(--text); }

textarea.notes { width: 100%; min-height: 110px; border: 1px solid var(--border); border-radius: 10px; padding: 10px; background: var(--surface-2); resize: vertical; }
.filters { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.filters select, .filters input[type="text"] { padding: 6px 10px; border-radius: 8px; border: 1px solid var(--border); background: var(--surface); }
.filters label { display: inline-flex; gap: 6px; align-items: center; font-size: 14px; }
.toast { position: fixed; bottom: 20px; left: 50%; transform: translateX(-50%); background: var(--text); color: var(--bg); padding: 10px 16px; border-radius: 10px; font-size: 14px; box-shadow: var(--shadow); opacity: 0; transition: opacity .2s; pointer-events: none; }
.toast.show { opacity: 1; }
.empty { padding: 40px; text-align: center; color: var(--muted); }
details.learn summary { cursor: pointer; font-weight: 600; }
ul.clean { margin: 8px 0 0; padding-left: 20px; }
ul.clean li { margin: 4px 0; }
.kbd-hint { font-family: var(--mono); font-size: 11px; color: var(--muted); }
@media print { .topbar, footer, .btn, .filters { display: none !important; } main { padding: 0; } .card { box-shadow: none; } }