:root {
  --bg: #f6f5f1;
  --panel: #ffffff;
  --panel-2: #f0eee8;
  --text: #1d1d1f;
  --muted: #64646b;
  --border: #e2dfd6;
  --accent: #2f5bd3;
  --accent-soft: #e6ecfb;
  --ok: #1d7f4e;
  --ok-soft: #e3f3ea;
  --bad: #b3261e;
  --bad-soft: #fbe9e7;
  --warn: #9a6200;
  --warn-soft: #fdf2dc;
  --violet: #6b4bc4;
  --violet-soft: #efe9fb;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(0,0,0,.05), 0 4px 16px rgba(0,0,0,.04);
  --font: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --serif: "Source Serif 4", Georgia, "Times New Roman", serif;
  --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #141416; --panel: #1c1c1f; --panel-2: #242428; --text: #ececee; --muted: #a0a0a8; --border: #33333a;
    --accent: #7b9cff; --accent-soft: #232c45; --ok: #5cc98f; --ok-soft: #1b3326; --bad: #ff8a80; --bad-soft: #3a1f1d;
    --warn: #f0b552; --warn-soft: #3a2f17; --violet: #b49cff; --violet-soft: #2a2340; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #141416; --panel: #1c1c1f; --panel-2: #242428; --text: #ececee; --muted: #a0a0a8; --border: #33333a;
  --accent: #7b9cff; --accent-soft: #232c45; --ok: #5cc98f; --ok-soft: #1b3326; --bad: #ff8a80; --bad-soft: #3a1f1d;
  --warn: #f0b552; --warn-soft: #3a2f17; --violet: #b49cff; --violet-soft: #2a2340; color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { background: var(--bg); color: var(--text); font-family: var(--font); font-size: 15.5px; line-height: 1.55; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.25; margin: 1.2em 0 .5em; }
h1 { font-size: 1.7rem; margin-top: 0; }
h2 { font-size: 1.3rem; }
h3 { font-size: 1.08rem; }
code { font-family: var(--mono); font-size: .88em; background: var(--panel-2); padding: .1em .35em; border-radius: 4px; }
pre { background: var(--panel-2); padding: 12px 14px; border-radius: 8px; overflow-x: auto; }
pre code { background: none; padding: 0; }
table { border-collapse: collapse; width: 100%; margin: 1em 0; font-size: .95em; }
th, td { border-bottom: 1px solid var(--border); padding: 7px 10px; text-align: left; vertical-align: top; }
th { font-weight: 600; color: var(--muted); font-size: .85em; text-transform: uppercase; letter-spacing: .03em; }
hr { border: 0; border-top: 1px solid var(--border); margin: 1.5em 0; }

/* ---------- layout ---------- */
.app { display: grid; grid-template-columns: 236px 1fr; min-height: 100vh; }
.sidebar { background: var(--panel); border-right: 1px solid var(--border); padding: 18px 14px; position: sticky; top: 0; height: 100vh; overflow-y: auto; display: flex; flex-direction: column; gap: 4px; }
.brand { font-weight: 700; font-size: 1.02rem; padding: 4px 10px 14px; display: flex; gap: 8px; align-items: center; }
.brand .logo { width: 28px; height: 28px; border-radius: 7px; background: var(--accent); color: #fff; display: grid; place-items: center; font-family: var(--serif); font-size: 17px; }
.nav a { display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 8px 10px; border-radius: 8px; color: var(--text); font-size: .95rem; }
.nav a:hover { background: var(--panel-2); text-decoration: none; }
.nav a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.nav .sep { height: 1px; background: var(--border); margin: 10px 4px; }
.badge { display: inline-block; min-width: 20px; padding: 1px 7px; border-radius: 999px; font-size: .75rem; font-weight: 600; background: var(--accent); color: #fff; text-align: center; }
.badge.muted { background: var(--panel-2); color: var(--muted); }
.sidebar .user { margin-top: auto; padding: 10px; font-size: .85rem; color: var(--muted); border-top: 1px solid var(--border); }
.main { padding: 28px 36px 60px; max-width: 1180px; width: 100%; min-width: 0; }
.app > div { min-width: 0; }
.prose table, .callout table { display: block; overflow-x: auto; }
.prose, .exercise, .card { overflow-wrap: anywhere; }
.main.wide { max-width: none; }
.topbar-mobile { display: none; }
@media (max-width: 860px) {
  .app { grid-template-columns: 1fr; }
  .sidebar { position: fixed; z-index: 30; left: 0; top: 0; width: 260px; transform: translateX(-100%); transition: transform .2s; }
  .sidebar.open { transform: none; box-shadow: var(--shadow); }
  .topbar-mobile { display: flex; align-items: center; gap: 12px; padding: 10px 16px; background: var(--panel); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 20; }
  .main { padding: 18px 16px 60px; }
}

/* ---------- componentes ---------- */
.card { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow); }
.card + .card { margin-top: 16px; }
.card h2:first-child, .card h3:first-child { margin-top: 0; }
.grid { display: grid; gap: 16px; }
.grid.cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid.cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid.cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
@media (max-width: 860px) { .grid.cols-2, .grid.cols-3, .grid.cols-4 { grid-template-columns: 1fr; } }
.row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.row.between { justify-content: space-between; }
.stack > * + * { margin-top: 12px; }
.muted { color: var(--muted); }
.small { font-size: .86rem; }
.tiny { font-size: .78rem; }
.right { text-align: right; }
.center { text-align: center; }
.mono { font-family: var(--mono); }
.hidden { display: none !important; }

.btn { display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--border); background: var(--panel); color: var(--text); padding: 8px 14px; border-radius: 8px; font: inherit; font-size: .93rem; cursor: pointer; font-weight: 500; }
.btn:hover { background: var(--panel-2); text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { filter: brightness(1.07); }
.btn.ok { background: var(--ok); border-color: var(--ok); color: #fff; }
.btn.danger { color: var(--bad); border-color: var(--bad); }
.btn.ghost { border-color: transparent; background: transparent; }
.btn.small { padding: 4px 10px; font-size: .84rem; }
.btn:disabled { opacity: .55; cursor: not-allowed; }
.btn-group { display: inline-flex; }
.btn-group .btn { border-radius: 0; }
.btn-group .btn:first-child { border-radius: 8px 0 0 8px; }
.btn-group .btn:last-child { border-radius: 0 8px 8px 0; }
.btn-group .btn + .btn { border-left: 0; }
.btn-group .btn.selected { background: var(--accent-soft); color: var(--accent); font-weight: 600; }

input[type=text], input[type=password], input[type=email], input[type=number], select, textarea {
  font: inherit; color: var(--text); background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; width: 100%;
}
input:focus, select:focus, textarea:focus { outline: 2px solid var(--accent-soft); border-color: var(--accent); }
textarea { resize: vertical; min-height: 80px; }
label.field { display: block; font-size: .86rem; color: var(--muted); margin-bottom: 10px; }
label.field > input, label.field > select, label.field > textarea { margin-top: 4px; }

.pill { display: inline-block; padding: 2px 9px; border-radius: 999px; font-size: .76rem; font-weight: 600; background: var(--panel-2); color: var(--muted); white-space: nowrap; }
.pill.ok { background: var(--ok-soft); color: var(--ok); }
.pill.bad { background: var(--bad-soft); color: var(--bad); }
.pill.warn { background: var(--warn-soft); color: var(--warn); }
.pill.accent { background: var(--accent-soft); color: var(--accent); }
.pill.violet { background: var(--violet-soft); color: var(--violet); }

.progress { height: 8px; background: var(--panel-2); border-radius: 999px; overflow: hidden; }
.progress > div { height: 100%; background: var(--accent); border-radius: 999px; }
.progress.ok > div { background: var(--ok); }

.stat { font-size: 1.9rem; font-weight: 700; line-height: 1.1; }
.stat-label { font-size: .8rem; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; }

.toast-host { position: fixed; bottom: 18px; right: 18px; display: flex; flex-direction: column; gap: 8px; z-index: 100; }
.toast { background: var(--text); color: var(--bg); padding: 10px 14px; border-radius: 8px; box-shadow: var(--shadow); max-width: 380px; font-size: .9rem; }
.toast.bad { background: var(--bad); color: #fff; }
.toast.ok { background: var(--ok); color: #fff; }

.modal-back { position: fixed; inset: 0; background: rgba(0,0,0,.35); display: grid; place-items: center; z-index: 90; padding: 16px; }
.modal { background: var(--panel); border-radius: 12px; padding: 22px; max-width: 560px; width: 100%; max-height: 90vh; overflow: auto; box-shadow: var(--shadow); }

/* ---------- ruta ---------- */
.tier-head { margin: 26px 0 10px; display: flex; align-items: baseline; gap: 10px; }
.units-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.unit-card { display: block; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; color: var(--text); position: relative; transition: border-color .15s, transform .15s; }
.unit-card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-1px); }
.unit-card .num { font-family: var(--serif); font-size: 1.5rem; font-weight: 600; color: var(--muted); }
.unit-card .title { font-weight: 600; margin: 2px 0 8px; }
.unit-card.locked, .unit-card.draft { opacity: .62; }
.unit-card.passed { border-left: 4px solid var(--ok); }
.unit-card.available { border-left: 4px solid var(--accent); }

/* ---------- lecciones ---------- */
.lesson-layout { display: grid; grid-template-columns: minmax(0, 1fr) 220px; gap: 32px; }
@media (max-width: 1100px) { .lesson-layout { grid-template-columns: 1fr; } .toc { display: none; } }
.prose { font-family: var(--serif); font-size: 1.08rem; line-height: 1.72; max-width: 760px; min-width: 0; }
.lesson-layout > * { min-width: 0; }
.katex-display > .katex { max-width: 100%; }
.prose h2, .prose h3 { font-family: var(--font); }
.prose p { margin: .7em 0; }
.prose li { margin: .25em 0; }
.prose table { font-family: var(--font); font-size: .9rem; }
.toc { position: sticky; top: 20px; align-self: start; font-size: .86rem; }
.toc a { display: block; color: var(--muted); padding: 3px 0; }
.toc a.l3 { padding-left: 12px; }
.callout { border-left: 4px solid var(--border); background: var(--panel); border-radius: 0 8px 8px 0; padding: 10px 16px; margin: 1.1em 0; font-family: var(--font); font-size: .98rem; box-shadow: var(--shadow); }
.callout-title { font-weight: 700; font-size: .8rem; text-transform: uppercase; letter-spacing: .05em; color: var(--muted); margin-bottom: 4px; }
.callout-definicion { border-color: var(--accent); }
.callout-definicion .callout-title { color: var(--accent); }
.callout-teorema, .callout-propiedad { border-color: var(--violet); }
.callout-teorema .callout-title, .callout-propiedad .callout-title { color: var(--violet); }
.callout-ejemplo { border-color: var(--ok); }
.callout-ejemplo .callout-title { color: var(--ok); }
.callout-atencion, .callout-error { border-color: var(--bad); }
.callout-atencion .callout-title, .callout-error .callout-title { color: var(--bad); }
.callout-llm { border-color: var(--warn); background: var(--warn-soft); }
.callout-llm .callout-title { color: var(--warn); }
.callout-intuicion { border-color: var(--violet); background: var(--violet-soft); }
.callout-resumen { border-color: var(--text); }
.callout-pensar { border-color: var(--warn); border-left-style: dashed; }
.callout-pensar .callout-title { color: var(--warn); }
.callout-objetivos { border-color: var(--accent); background: var(--accent-soft); }
.callout-demostracion { border-color: var(--muted); background: var(--panel-2); }
details.solution, details.verify-block { border: 1px solid var(--border); border-radius: 8px; padding: 8px 14px; margin: 1em 0; font-family: var(--font); font-size: .95rem; background: var(--panel); }
details > summary { cursor: pointer; font-weight: 600; color: var(--accent); }
details.verify-block > summary { color: var(--muted); font-weight: 500; font-size: .86rem; }
.reflection { border: 1px dashed var(--violet); border-radius: 8px; padding: 12px 16px; margin: 1.2em 0; font-family: var(--font); font-size: .97rem; }
.reflection .callout-title { color: var(--violet); }
.embedded-exercise { margin: 1.4em 0; font-family: var(--font); font-size: 1rem; }
.calc-snippet { margin: 1em 0; }
.calc-snippet pre { margin-bottom: 6px; }

/* ---------- ejercicios ---------- */
.exercise { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow); }
.exercise .ex-head { display: flex; justify-content: space-between; gap: 10px; align-items: center; margin-bottom: 8px; flex-wrap: wrap; }
.exercise .statement { font-size: 1.05rem; margin: 6px 0 14px; }
.exercise .part { margin: 14px 0; }
.exercise .part-label { margin-bottom: 6px; }
.answer-row { display: flex; gap: 8px; align-items: center; }
.answer-row input { font-family: var(--mono); font-size: 1rem; }
.preview { min-height: 26px; margin-top: 4px; font-size: .95rem; color: var(--muted); }
.preview.err { color: var(--bad); font-size: .85rem; }
.options { display: flex; flex-direction: column; gap: 6px; }
.option { display: flex; gap: 10px; align-items: flex-start; border: 1px solid var(--border); border-radius: 8px; padding: 8px 12px; cursor: pointer; background: var(--panel); }
.option:hover { border-color: var(--accent); }
.option.selected { border-color: var(--accent); background: var(--accent-soft); }
.option.correct { border-color: var(--ok); background: var(--ok-soft); }
.option.wrong { border-color: var(--bad); background: var(--bad-soft); }
.option input { margin-top: 5px; }
.part-result { margin-top: 8px; padding: 8px 12px; border-radius: 8px; font-size: .93rem; }
.part-result.ok { background: var(--ok-soft); color: var(--ok); }
.part-result.bad { background: var(--bad-soft); color: var(--bad); }
.part-result.invalid { background: var(--warn-soft); color: var(--warn); }
.part-result .expected { color: var(--text); margin-top: 4px; }
.confidence { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; font-size: .88rem; color: var(--muted); margin-top: 12px; }
.hints { margin-top: 10px; }
.hint { background: var(--warn-soft); border-radius: 8px; padding: 8px 12px; margin-top: 8px; font-size: .95rem; }
.steps { margin-top: 14px; border-top: 1px solid var(--border); padding-top: 10px; }
.step { display: grid; grid-template-columns: 30px 1fr; gap: 8px; margin: 10px 0; }
.step .n { width: 24px; height: 24px; border-radius: 50%; background: var(--accent-soft); color: var(--accent); font-weight: 700; display: grid; place-items: center; font-size: .8rem; }
.ex-actions { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 14px; }
.syntax-help { font-size: .82rem; color: var(--muted); }
.syntax-help code { font-size: .8rem; }

/* ---------- examen ---------- */
.exam-bar { position: sticky; top: 0; z-index: 15; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 10px 16px; display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-bottom: 16px; box-shadow: var(--shadow); flex-wrap: wrap; }
.timer { font-family: var(--mono); font-size: 1.35rem; font-weight: 700; }
.timer.low { color: var(--bad); }
.qnav { display: flex; gap: 4px; flex-wrap: wrap; }
.qnav button { width: 30px; height: 30px; border-radius: 6px; border: 1px solid var(--border); background: var(--panel); cursor: pointer; font: inherit; font-size: .8rem; color: var(--text); }
.qnav button.answered { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }
.qnav button.current { outline: 2px solid var(--accent); }
.qnav button.ok { background: var(--ok-soft); border-color: var(--ok); color: var(--ok); }
.qnav button.bad { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }

/* ---------- repaso ---------- */
.flash { min-height: 220px; display: flex; flex-direction: column; justify-content: center; font-size: 1.12rem; }
.flash .back { border-top: 1px dashed var(--border); margin-top: 14px; padding-top: 14px; }
.rate-buttons { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-top: 16px; }
.rate-buttons .btn { justify-content: center; flex-direction: column; gap: 0; }
.rate-buttons .btn small { font-weight: 400; color: var(--muted); font-size: .75rem; }

/* ---------- calculadora ---------- */
.calc-layout { display: grid; grid-template-columns: minmax(0, 1fr) 320px; gap: 18px; }
@media (max-width: 1100px) { .calc-layout { grid-template-columns: 1fr; } }
.calc-editor { font-family: var(--mono); font-size: .98rem; min-height: 220px; line-height: 1.6; }
.calc-result { border-bottom: 1px solid var(--border); padding: 10px 0; }
.calc-result .in { font-family: var(--mono); font-size: .85rem; color: var(--muted); }
.calc-result .out { overflow-x: auto; padding: 4px 0; }
.calc-result .num { font-family: var(--mono); font-size: .85rem; color: var(--muted); }
.calc-result.err .out { color: var(--bad); font-size: .9rem; }
.help-group h4 { margin: 14px 0 6px; font-size: .9rem; }
.help-item { font-size: .82rem; margin: 6px 0; }
.help-item code { cursor: pointer; }
.help-item code:hover { background: var(--accent-soft); }
.calc-help { max-height: 75vh; overflow-y: auto; }

/* ---------- gráficos ---------- */
svg.chart text { fill: var(--muted); font-size: 11px; font-family: var(--font); }
svg.chart .axis { stroke: var(--border); }
svg.chart .bar { fill: var(--accent); }
svg.chart .bar.ok { fill: var(--ok); }
svg.chart .line { fill: none; stroke-width: 2; }
svg.chart .grid { stroke: var(--border); stroke-dasharray: 2 3; }
.heat { display: grid; grid-template-columns: repeat(13, 14px); grid-auto-flow: column; grid-template-rows: repeat(7, 14px); gap: 3px; }
.heat div { border-radius: 3px; background: var(--panel-2); }

/* ---------- login ---------- */
.login-wrap { min-height: 100vh; display: grid; place-items: center; padding: 16px; }
.login-card { width: 100%; max-width: 380px; }

.katex { font-size: 1.06em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.math.block { display: block; }
.err-box { background: var(--bad-soft); color: var(--bad); border-radius: 8px; padding: 10px 14px; }
.ok-box { background: var(--ok-soft); color: var(--ok); border-radius: 8px; padding: 10px 14px; }
.info-box { background: var(--accent-soft); color: var(--text); border-radius: 8px; padding: 10px 14px; }
.kbd { font-family: var(--mono); font-size: .8em; border: 1px solid var(--border); border-bottom-width: 2px; border-radius: 4px; padding: 0 5px; }