:root {
  --ink: #17212b;
  --muted: #526273;
  --paper: #ffffff;
  --card: #f5f8fb;
  --card-2: #eef3f8;
  --line: #d7e0e8;
  --green: #0c7a62;
  --green-soft: rgba(12, 122, 98, 0.1);
  --copper: #a15d22;
  --copper-soft: rgba(161, 93, 34, 0.1);
  --blue: #1d5c96;
  --blue-soft: rgba(29, 92, 150, 0.08);
  --term: #10202c;
  --term-ink: #e7eef4;
  --term-dim: #8aa0b3;
  --term-ok: #7dcea0;
  --top: rgba(255, 255, 255, 0.94);
  --rail: #f7fafc;
  --solid: #0c7a62;
  --solid-ink: #ffffff;
  --wash: rgba(12, 122, 98, 0.07);
  --shadow: 0 8px 24px rgba(23, 33, 43, 0.06);
  color-scheme: light;
  font-family: ui-sans-serif, "Segoe UI", Helvetica, Arial, sans-serif;
}

html[data-theme="dark"] {
  --ink: #e8eef4;
  --muted: #93a4b5;
  --paper: #0c1218;
  --card: #16202b;
  --card-2: #1c2936;
  --line: #2c3d4e;
  --green: #3dbea0;
  --green-soft: rgba(61, 190, 160, 0.14);
  --copper: #e0a36a;
  --copper-soft: rgba(224, 163, 106, 0.14);
  --blue: #8eb7e0;
  --blue-soft: rgba(142, 183, 224, 0.1);
  --term: #0a1016;
  --term-ink: #e7eef4;
  --term-dim: #7f93a6;
  --term-ok: #7dcea0;
  --top: rgba(12, 18, 24, 0.92);
  --rail: rgba(14, 20, 28, 0.65);
  --solid: #3dbea0;
  --solid-ink: #06241c;
  --wash: rgba(61, 190, 160, 0.08);
  --shadow: 0 10px 28px rgba(0, 0, 0, 0.28);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; background: var(--paper); color: var(--ink); }
body {
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background:
    radial-gradient(900px 420px at 0% -10%, var(--wash), transparent 60%),
    var(--paper);
}
button, input, summary { font: inherit; }
button { cursor: pointer; }
code, .mono, .term-out, .term-in { font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace; }

.top {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px 12px;
  padding: 12px 18px;
  border-bottom: 1px solid var(--line);
  background: var(--top);
  position: sticky;
  top: 0;
  z-index: 2;
}
.brand h1 { margin: 0; font-size: 1.15rem; font-weight: 650; letter-spacing: 0.08em; }
.eyebrow { margin: 0; color: var(--green); font-size: 0.68rem; letter-spacing: 0.12em; text-transform: uppercase; }
.primary { display: flex; gap: 6px; }
.primary button {
  background: transparent;
  color: var(--muted);
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 7px 12px;
}
.primary button[aria-current="page"] {
  color: var(--ink);
  background: var(--card);
  border-color: var(--line);
}
.search { display: flex; flex-direction: column; gap: 2px; min-width: 140px; flex: 1 1 160px; max-width: 260px; color: var(--muted); font-size: 0.72rem; }
.session { display: flex; align-items: center; gap: 10px; margin-left: auto; }
.search input {
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 8px;
  padding: 8px 10px;
  color: var(--ink);
}
.meter { margin: 0; color: var(--muted); font-size: 0.82rem; white-space: nowrap; }
.tools { position: relative; }
.tools summary {
  list-style: none;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 7px 10px;
  color: var(--muted);
  cursor: pointer;
}
.tools summary::-webkit-details-marker { display: none; }
.tools[open] { display: flex; flex-direction: column; gap: 6px; }
.ghost, .solid, .quiet { border-radius: 8px; padding: 8px 12px; }
.ghost { background: var(--card); border: 1px solid var(--line); color: var(--ink); }
.solid { background: var(--solid); color: var(--solid-ink); border: 0; font-weight: 650; }
.theme {
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 999px;
  padding: 7px 12px;
  white-space: nowrap;
}
.theme[aria-pressed="true"] { background: var(--card-2); }
.quiet { background: transparent; border: 0; color: var(--blue); padding-left: 0; }

.shell { display: grid; grid-template-columns: 280px 1fr; flex: 1; min-height: 0; }
.rail, #stage { overflow: auto; min-height: 0; }
.rail { border-right: 1px solid var(--line); padding: 14px 12px 24px; background: var(--rail); }
.section-label {
  margin: 14px 8px 6px;
  color: var(--muted);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}
.rail button.nav {
  display: block;
  width: 100%;
  text-align: left;
  background: transparent;
  border: 0;
  border-radius: 8px;
  padding: 8px 10px;
  color: var(--ink);
}
.rail button.nav[aria-current="page"], .rail button.lesson.active {
  background: var(--green-soft);
  color: var(--ink);
}
.track { margin-top: 8px; }
.track-name { display: flex; justify-content: space-between; gap: 8px; padding: 6px 8px; font-weight: 650; font-size: 0.92rem; }
.track-count { color: var(--muted); font-weight: 400; font-size: 0.78rem; }
.lesson {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  width: calc(100% - 10px);
  margin-left: 10px;
  text-align: left;
  background: transparent;
  border: 0;
  border-radius: 8px;
  padding: 6px 8px;
  color: var(--muted);
}
.lesson .mark { width: 1.1rem; color: var(--green); }
.stage { padding: 28px 36px 80px; max-width: 920px; }
.stage.wide { max-width: 1180px; }
.stage h2 { margin: 0 0 8px; font-size: 1.8rem; letter-spacing: -0.03em; }
.lede { font-size: 1.05rem; color: var(--muted); max-width: 68ch; }
.path { display: grid; gap: 10px; margin-top: 22px; }
.station {
  display: grid;
  grid-template-columns: 52px 1fr auto;
  gap: 12px;
  align-items: center;
  width: 100%;
  text-align: left;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 14px;
  color: inherit;
}
.station:hover { border-color: var(--green); }
.ord {
  width: 40px; height: 40px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--green-soft); color: var(--green); font-weight: 700;
}
.station small { color: var(--muted); }
.pill {
  display: inline-block;
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--green);
  background: var(--green-soft);
  border-radius: 999px;
  padding: 3px 8px;
}
.group-title { margin: 26px 0 10px; font-size: 0.78rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--muted); }
.block h3 { margin: 22px 0 8px; font-size: 1.05rem; }
.block p, .block li { line-height: 1.55; }
.block ul { margin: 8px 0; padding-left: 1.2rem; }
pre {
  background: var(--term);
  color: var(--term-ink);
  padding: 12px 14px;
  border-radius: 10px;
  overflow: auto;
  border: 1px solid var(--line);
}
.callout {
  border-left: 3px solid var(--blue);
  background: var(--blue-soft);
  padding: 10px 12px;
  border-radius: 0 10px 10px 0;
}
.callout.caution { border-color: var(--copper); background: var(--copper-soft); }
.objectives, .lab, .quiz {
  margin-top: 22px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px 16px;
}
.objectives { margin-top: 0; }
.term {
  margin-top: 22px;
  background: var(--term);
  color: var(--term-ink);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px 16px;
}
.term-log { min-height: 140px; white-space: pre-wrap; margin: 0 0 10px; }
.term form { display: flex; gap: 8px; }
.term input {
  flex: 1;
  background: transparent;
  border: 0;
  border-bottom: 1px solid #345066;
  color: var(--term-ink);
  padding: 6px 0;
}
.prompt { color: var(--term-ok); }
.ok { color: var(--term-ok); }
.dim { color: var(--term-dim); }
.choices { display: grid; gap: 8px; margin: 12px 0; }
.choices label {
  display: flex; gap: 8px; align-items: flex-start;
  border: 1px solid var(--line); border-radius: 8px; padding: 8px 10px;
  background: var(--card-2);
}
.choices label.right { background: var(--green-soft); border-color: var(--green); }
.choices label.wrong { background: var(--copper-soft); border-color: var(--copper); }
.why { color: var(--muted); margin: 4px 0 0 1.4rem; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.pass { color: var(--green); font-weight: 700; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 12px; }
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px 14px 12px;
  border-top: 3px solid var(--green);
  box-shadow: var(--shadow);
}
.card h3 { margin: 0 0 6px; font-size: 1.02rem; }
.card p { margin: 6px 0; color: var(--muted); line-height: 1.45; }
.card a { color: var(--ink); text-decoration: none; }
.card a:hover { color: var(--green); }
.card .mono { color: var(--blue); }
.mono { font-size: 0.82rem; }
.check { display: flex; gap: 10px; align-items: flex-start; margin: 10px 0; line-height: 1.45; }
.hidden { display: none; }

@media (max-width: 860px) {
  .search { margin-left: 0; max-width: none; }
  .shell { grid-template-columns: 1fr; grid-template-rows: 32vh 1fr; }
  .rail { border-right: 0; border-bottom: 1px solid var(--line); }
  .stage { padding: 20px 16px 64px; }
}