/* ==========================================================================
   MasteryLeap — Design System
   Themes: light (default tokens) + dark ([data-theme="dark"])
   ========================================================================== */

:root {
  --bg: #f5f7ff;
  --bg-2: #eaefff;
  --surface: #ffffff;
  --surface-2: #f1f4fd;
  --glass: rgba(255, 255, 255, 0.78);
  --border: #dde3f4;
  --border-strong: #c5cdea;
  --text: #0e1633;
  --text-2: #36406a;
  --muted: #5b6590;
  --accent: #0891b2;      /* electric cyan */
  --accent-2: #7c3aed;    /* violet */
  --accent-3: #d97706;    /* amber */
  --pink: #db2777;
  --ok: #059669;
  --danger: #dc2626;
  --grad: linear-gradient(120deg, #06b6d4 0%, #7c3aed 55%, #db2777 100%);
  --grad-soft: linear-gradient(135deg, rgba(8,145,178,.10), rgba(124,58,237,.10));
  --shadow-sm: 0 1px 2px rgba(15, 23, 60, .06), 0 2px 8px rgba(15, 23, 60, .05);
  --shadow: 0 10px 30px -10px rgba(30, 40, 100, .18), 0 2px 6px rgba(30, 40, 100, .06);
  --shadow-lg: 0 30px 60px -20px rgba(40, 30, 120, .28);
  --glow: 0 0 0 rgba(0,0,0,0);

  /* simulator tokens */
  --sim-bg: #f8faff;
  --sim-grid: rgba(80, 100, 180, .10);
  --wire: #334068;
  --electron: #0891b2;
  --conv: #d97706;
  --hi: #059669;
  --lo: #9aa3c4;

  --radius: 16px;
  --radius-sm: 10px;
  --radius-lg: 24px;
  --maxw: 1200px;
  --font-head: "Space Grotesk", "Segoe UI", system-ui, sans-serif;
  --font-body: "Inter", "Segoe UI", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, Consolas, monospace;
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #060a18;
  --bg-2: #0a1026;
  --surface: #0f1631;
  --surface-2: #141d3d;
  --glass: rgba(14, 21, 48, 0.72);
  --border: rgba(130, 155, 255, .14);
  --border-strong: rgba(130, 155, 255, .28);
  --text: #e9edff;
  --text-2: #c3cbee;
  --muted: #8f9acb;
  --accent: #22d3ee;
  --accent-2: #a78bfa;
  --accent-3: #fbbf24;
  --pink: #f472b6;
  --ok: #34d399;
  --danger: #f87171;
  --grad: linear-gradient(120deg, #22d3ee 0%, #a78bfa 55%, #f472b6 100%);
  --grad-soft: linear-gradient(135deg, rgba(34,211,238,.10), rgba(167,139,250,.10));
  --shadow-sm: 0 1px 2px rgba(0,0,0,.4);
  --shadow: 0 12px 34px -12px rgba(0,0,0,.6);
  --shadow-lg: 0 40px 80px -30px rgba(0,0,0,.8);
  --glow: 0 0 24px rgba(34, 211, 238, .25);

  --sim-bg: #0a1130;
  --sim-grid: rgba(120, 150, 255, .08);
  --wire: #8ea0d8;
  --electron: #22d3ee;
  --conv: #fbbf24;
  --hi: #34d399;
  --lo: #3b4775;
  color-scheme: dark;
}

/* ---------- Reset & base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 16.5px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  transition: background .35s ease, color .35s ease;
}
img, svg, canvas { max-width: 100%; display: block; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
h1, h2, h3, h4 { font-family: var(--font-head); line-height: 1.15; margin: 0 0 .5em; letter-spacing: -0.02em; }
h1 { font-size: clamp(2.2rem, 5.2vw, 4rem); font-weight: 700; }
h2 { font-size: clamp(1.7rem, 3.4vw, 2.5rem); font-weight: 700; }
h3 { font-size: 1.3rem; font-weight: 600; }
h4 { font-size: 1.05rem; font-weight: 600; }
p { margin: 0 0 1em; color: var(--text-2); }
code, kbd, .mono { font-family: var(--font-mono); font-size: .92em; }
::selection { background: color-mix(in srgb, var(--accent) 30%, transparent); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 6px; }
.skip-link { position: absolute; left: -999px; top: 8px; background: var(--surface); padding: 8px 14px; border-radius: 8px; z-index: 999; }
.skip-link:focus { left: 8px; }

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }
.section { padding: clamp(56px, 8vw, 110px) 0; position: relative; }
.section-head { max-width: 720px; margin-bottom: 44px; }
.section-head.center { margin-left: auto; margin-right: auto; text-align: center; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--font-mono); font-size: .78rem; font-weight: 600;
  letter-spacing: .14em; text-transform: uppercase; color: var(--accent);
  margin-bottom: 14px;
}
.eyebrow::before { content: ""; width: 18px; height: 2px; background: var(--grad); border-radius: 2px; }
.grad-text { background: var(--grad); -webkit-background-clip: text; background-clip: text; color: transparent; }
.lead { font-size: 1.15rem; color: var(--muted); }
.muted { color: var(--muted); }
.center { text-align: center; }
.hidden { display: none !important; }

/* background decoration */
.bg-grid {
  position: absolute; inset: 0; pointer-events: none; z-index: 0;
  background-image:
    linear-gradient(var(--sim-grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--sim-grid) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: radial-gradient(ellipse at center, #000 30%, transparent 75%);
}
.blob { position: absolute; border-radius: 50%; filter: blur(80px); opacity: .35; pointer-events: none; z-index: 0; }
[data-theme="dark"] .blob { opacity: .28; }

/* ---------- Buttons ---------- */
.btn {
  --b: var(--surface);
  display: inline-flex; align-items: center; justify-content: center; gap: 9px;
  padding: 12px 22px; border-radius: 999px; border: 1px solid var(--border-strong);
  background: var(--b); color: var(--text);
  font-family: var(--font-head); font-weight: 600; font-size: .98rem;
  cursor: pointer; transition: transform .18s ease, box-shadow .2s ease, background .2s, border-color .2s;
  text-decoration: none !important; white-space: nowrap;
}
.btn:hover { transform: translateY(-2px); box-shadow: var(--shadow); border-color: var(--accent); }
.btn:active { transform: translateY(0); }
.btn-primary { background: var(--grad); color: #fff; border: none; box-shadow: 0 10px 30px -10px rgba(124, 58, 237, .6); }
.btn-primary:hover { box-shadow: 0 16px 40px -12px rgba(124, 58, 237, .75), var(--glow); }
.btn-ghost { background: transparent; }
.btn-sm { padding: 8px 15px; font-size: .88rem; }
.btn-lg { padding: 16px 30px; font-size: 1.06rem; }
.btn[disabled] { opacity: .45; cursor: not-allowed; transform: none; box-shadow: none; }
.icon-btn {
  width: 40px; height: 40px; border-radius: 12px; display: inline-grid; place-items: center;
  background: var(--surface-2); border: 1px solid var(--border); color: var(--text); cursor: pointer;
  transition: border-color .2s, transform .2s;
}
.icon-btn:hover { border-color: var(--accent); transform: rotate(-8deg); }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: var(--glass); backdrop-filter: saturate(1.4) blur(16px); -webkit-backdrop-filter: saturate(1.4) blur(16px);
  border-bottom: 1px solid var(--border);
}
.nav { display: flex; align-items: center; gap: 18px; height: 68px; }
.brand { display: flex; align-items: center; gap: 10px; font-family: var(--font-head); font-weight: 700; font-size: 1.18rem; color: var(--text); letter-spacing: -0.02em; }
.brand:hover { text-decoration: none; }
.brand svg { width: 34px; height: 34px; }
.brand small { display: block; font-size: .62rem; letter-spacing: .2em; color: var(--muted); font-weight: 500; margin-top: -4px; }
.nav-links { display: flex; gap: 4px; margin-left: auto; list-style: none; padding: 0; margin-top: 0; margin-bottom: 0; }
.nav-links a {
  display: block; padding: 8px 13px; border-radius: 10px; color: var(--text-2);
  font-weight: 500; font-size: .94rem;
}
.nav-links a:hover { background: var(--surface-2); color: var(--text); text-decoration: none; }
.nav-links a.active { color: var(--accent); background: color-mix(in srgb, var(--accent) 10%, transparent); }
.nav-tools { display: flex; align-items: center; gap: 10px; }
.xp-pill {
  display: inline-flex; align-items: center; gap: 6px; padding: 6px 12px; border-radius: 999px;
  background: var(--grad-soft); border: 1px solid var(--border); font-family: var(--font-mono); font-size: .8rem; font-weight: 600; color: var(--text);
}
.xp-pill:hover { text-decoration: none; border-color: var(--accent); }
.menu-btn { display: none; }
.theme-toggle .sun { display: none; }
[data-theme="dark"] .theme-toggle .sun { display: block; }
[data-theme="dark"] .theme-toggle .moon { display: none; }
.read-progress { position: absolute; left: 0; bottom: -1px; height: 2px; background: var(--grad); width: 0; transition: width .1s linear; }

@media (max-width: 920px) {
  .menu-btn { display: inline-grid; }
  .nav-links {
    position: absolute; top: 68px; left: 0; right: 0; flex-direction: column; gap: 0;
    background: var(--surface); border-bottom: 1px solid var(--border); padding: 8px 16px 16px;
    display: none; box-shadow: var(--shadow);
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 12px; }
  .xp-pill span.lbl { display: none; }
}

/* ---------- Footer ---------- */
.site-footer { border-top: 1px solid var(--border); background: var(--bg-2); padding: 56px 0 28px; margin-top: 40px; }
.footer-grid { display: grid; grid-template-columns: 1.6fr 1fr 1fr 1fr; gap: 32px; }
.footer-grid h4 { font-size: .85rem; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.footer-grid ul { list-style: none; padding: 0; margin: 0; }
.footer-grid li { margin: 6px 0; }
.footer-grid a { color: var(--text-2); }
.footer-bottom { margin-top: 40px; padding-top: 20px; border-top: 1px solid var(--border); display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px; font-size: .88rem; color: var(--muted); }
@media (max-width: 760px) { .footer-grid { grid-template-columns: 1fr 1fr; } }

/* ---------- Cards & grids ---------- */
.grid { display: grid; gap: 22px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 980px) { .grid-4 { grid-template-columns: repeat(2, 1fr); } .grid-3 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 640px) { .grid-4, .grid-3, .grid-2 { grid-template-columns: 1fr; } }

.card {
  position: relative; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow-sm);
  transition: transform .25s ease, box-shadow .25s ease, border-color .25s;
}
.card.hover:hover { transform: translateY(-5px); box-shadow: var(--shadow-lg); border-color: var(--border-strong); }
.card h3 { margin-bottom: 8px; }
.card p:last-child { margin-bottom: 0; }
.card-icon {
  width: 52px; height: 52px; border-radius: 14px; display: grid; place-items: center;
  font-size: 1.5rem; margin-bottom: 16px; background: var(--grad-soft); border: 1px solid var(--border);
}
.chip {
  display: inline-flex; align-items: center; gap: 6px; padding: 4px 11px; border-radius: 999px;
  font-size: .76rem; font-weight: 600; font-family: var(--font-mono);
  background: var(--surface-2); border: 1px solid var(--border); color: var(--text-2);
}
.chip.ok { color: var(--ok); border-color: color-mix(in srgb, var(--ok) 40%, transparent); background: color-mix(in srgb, var(--ok) 10%, transparent); }
.chip.acc { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 40%, transparent); background: color-mix(in srgb, var(--accent) 10%, transparent); }

/* Track colors */
.t1 { --tc: #06b6d4; } .t2 { --tc: #8b5cf6; } .t3 { --tc: #f59e0b; } .t4 { --tc: #ec4899; }

/* ---------- Hero ---------- */
.hero { position: relative; overflow: hidden; padding: clamp(60px, 9vw, 120px) 0 clamp(60px, 8vw, 100px); }
.hero canvas.hero-canvas { position: absolute; inset: 0; width: 100%; height: 100%; z-index: 0; opacity: .9; }
.hero-inner { position: relative; z-index: 2; display: grid; grid-template-columns: 1.05fr .95fr; gap: 40px; align-items: center; }
.hero h1 { margin-bottom: 22px; }
.hero .lead { max-width: 560px; margin-bottom: 30px; }
.hero-ctas { display: flex; gap: 14px; flex-wrap: wrap; }
.hero-badges { display: flex; gap: 22px; margin-top: 36px; flex-wrap: wrap; }
.hero-badges div { font-size: .9rem; color: var(--muted); }
.hero-badges strong { display: block; font-family: var(--font-head); font-size: 1.7rem; color: var(--text); }
.hero-visual { position: relative; }
.hero-visual .card { padding: 0; overflow: hidden; box-shadow: var(--shadow-lg); }
.float { animation: float 6s ease-in-out infinite; }
@keyframes float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-10px); } }
@media (max-width: 920px) { .hero-inner { grid-template-columns: 1fr; } }

/* ---------- Track cards ---------- */
.track-card { border-top: 3px solid var(--tc); overflow: hidden; display: flex; flex-direction: column; }
.track-card .num { font-family: var(--font-mono); font-size: .78rem; color: var(--tc); font-weight: 700; letter-spacing: .1em; }
.track-card ul { padding-left: 18px; margin: 6px 0 18px; color: var(--muted); font-size: .92rem; }
.track-card .foot { margin-top: auto; display: flex; align-items: center; justify-content: space-between; gap: 10px; }
.ring { width: 52px; height: 52px; }
.ring circle { fill: none; stroke-width: 5; }
.ring .bgc { stroke: var(--surface-2); }
.ring .fg { stroke: var(--tc, var(--accent)); stroke-linecap: round; transform: rotate(-90deg); transform-origin: center; transition: stroke-dashoffset 1s ease; }
.ring text { font-family: var(--font-mono); font-size: 11px; font-weight: 700; fill: var(--text); }
.track-art { height: 90px; margin: -26px -26px 18px; background: color-mix(in srgb, var(--tc) 10%, var(--surface-2)); display: grid; place-items: center; font-size: 2.4rem; position: relative; overflow: hidden; }
.track-art::after { content: ""; position: absolute; inset: 0; background-image: linear-gradient(color-mix(in srgb, var(--tc) 14%, transparent) 1px, transparent 1px), linear-gradient(90deg, color-mix(in srgb, var(--tc) 14%, transparent) 1px, transparent 1px); background-size: 18px 18px; }
.track-art span { position: relative; z-index: 1; filter: drop-shadow(0 4px 12px color-mix(in srgb, var(--tc) 60%, transparent)); }

/* ---------- Steps (how it works) ---------- */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; counter-reset: step; }
.step { padding: 22px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--border); position: relative; }
.step::before { counter-increment: step; content: "0" counter(step); font-family: var(--font-mono); font-weight: 700; font-size: .8rem; color: var(--accent); }
.step h4 { margin: 8px 0 4px; }
.step p { margin: 0; font-size: .92rem; color: var(--muted); }
@media (max-width: 860px) { .steps { grid-template-columns: 1fr 1fr; } }
@media (max-width: 520px) { .steps { grid-template-columns: 1fr; } }

/* ---------- Page header ---------- */
.page-hero { position: relative; padding: 64px 0 40px; overflow: hidden; border-bottom: 1px solid var(--border); background: var(--bg-2); }
.page-hero .container { position: relative; z-index: 1; }
.page-hero h1 { font-size: clamp(2rem, 4.4vw, 3.1rem); }
.breadcrumbs { font-size: .86rem; color: var(--muted); margin-bottom: 14px; }
.breadcrumbs a { color: var(--muted); }

/* ---------- Course map ---------- */
.track-block { margin-bottom: 56px; }
.track-block-head { display: flex; align-items: center; gap: 18px; margin-bottom: 22px; flex-wrap: wrap; }
.track-badge { width: 56px; height: 56px; border-radius: 16px; display: grid; place-items: center; font-size: 1.6rem; background: color-mix(in srgb, var(--tc) 16%, transparent); border: 1px solid color-mix(in srgb, var(--tc) 40%, transparent); }
.lesson-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 16px; }
.lesson-card { display: flex; gap: 14px; align-items: flex-start; padding: 18px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--border); color: var(--text); transition: transform .2s, border-color .2s, box-shadow .2s; }
.lesson-card:hover { text-decoration: none; transform: translateY(-3px); border-color: var(--tc); box-shadow: var(--shadow); }
.lesson-card .ln { flex: none; width: 38px; height: 38px; border-radius: 11px; display: grid; place-items: center; font-family: var(--font-mono); font-weight: 700; font-size: .85rem; background: color-mix(in srgb, var(--tc) 14%, transparent); color: var(--tc); }
.lesson-card.done .ln { background: var(--ok); color: #fff; }
.lesson-card h4 { margin: 0 0 4px; font-size: 1rem; }
.lesson-card small { color: var(--muted); font-size: .8rem; }

/* ---------- Lesson layout ---------- */
.lesson-wrap { display: grid; grid-template-columns: 280px minmax(0, 1fr); gap: 40px; padding-top: 36px; padding-bottom: 60px; }
.lesson-side { position: sticky; top: 88px; align-self: start; max-height: calc(100vh - 110px); overflow: auto; padding-right: 4px; }
.lesson-side h4 { font-size: .78rem; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); margin: 18px 0 10px; }
.side-list { list-style: none; padding: 0; margin: 0; }
.side-list a { display: flex; gap: 10px; align-items: center; padding: 8px 10px; border-radius: 10px; color: var(--text-2); font-size: .9rem; }
.side-list a:hover { background: var(--surface-2); text-decoration: none; }
.side-list a.cur { background: color-mix(in srgb, var(--tc) 14%, transparent); color: var(--text); font-weight: 600; }
.side-list .dot { width: 22px; height: 22px; flex: none; border-radius: 7px; display: grid; place-items: center; font-size: .7rem; font-family: var(--font-mono); background: var(--surface-2); border: 1px solid var(--border); }
.side-list a.done .dot { background: var(--ok); border-color: var(--ok); color: #fff; }
.toc a { font-size: .86rem; padding: 5px 10px; }
@media (max-width: 980px) { .lesson-wrap { grid-template-columns: 1fr; } .lesson-side { position: static; max-height: none; order: 2; border-top: 1px solid var(--border); padding-top: 20px; } .lesson-side .toc-wrap { display: none; } }
@media (max-width: 640px) { .container { padding: 0 16px; } .hook { font-size: 1.12rem; padding: 20px; } .card { padding: 20px; } }

.lesson-main { min-width: 0; }
.lesson-title { margin-bottom: 26px; }
.lesson-title h1 { font-size: clamp(2rem, 4vw, 2.9rem); margin-bottom: 12px; }
.lesson-meta { display: flex; gap: 10px; flex-wrap: wrap; }
.block { margin: 0 0 30px; scroll-margin-top: 90px; }
.block-label { display: inline-flex; align-items: center; gap: 8px; font-family: var(--font-mono); font-size: .74rem; font-weight: 700; letter-spacing: .14em; text-transform: uppercase; color: var(--tc, var(--accent)); margin-bottom: 10px; }
.block-label i { font-style: normal; width: 26px; height: 26px; border-radius: 8px; display: grid; place-items: center; background: color-mix(in srgb, var(--tc, var(--accent)) 14%, transparent); font-size: .85rem; }
.hook {
  padding: 26px 28px; border-radius: var(--radius-lg); background: var(--grad-soft); border: 1px solid var(--border);
  font-family: var(--font-head); font-size: 1.3rem; line-height: 1.45; color: var(--text); position: relative; overflow: hidden;
}
.hook::after { content: "?"; position: absolute; right: 18px; bottom: -34px; font-size: 9rem; font-weight: 700; opacity: .07; }
.objectives { list-style: none; padding: 0; margin: 0; display: grid; gap: 10px; }
.objectives li { display: flex; gap: 12px; align-items: flex-start; padding: 12px 16px; background: var(--surface); border: 1px solid var(--border); border-radius: 12px; }
.objectives li::before { content: "✓"; flex: none; width: 22px; height: 22px; border-radius: 50%; display: grid; place-items: center; font-size: .75rem; font-weight: 700; color: #fff; background: var(--tc, var(--accent)); margin-top: 2px; }
.recall { padding: 14px 18px; border-left: 3px solid var(--accent-2); background: color-mix(in srgb, var(--accent-2) 8%, transparent); border-radius: 0 12px 12px 0; color: var(--text-2); }
.concept { margin-bottom: 40px; }
.concept h2 { font-size: clamp(1.4rem, 2.6vw, 1.85rem); margin-bottom: 14px; }
.concept .body p, .concept .body li { color: var(--text-2); }
.concept .body ul { padding-left: 20px; }
.callout { padding: 16px 18px; border-radius: 14px; border: 1px solid var(--border); background: var(--surface); margin: 16px 0; display: flex; gap: 12px; }
.callout .ic { font-size: 1.3rem; flex: none; }
.callout.tip { border-color: color-mix(in srgb, var(--ok) 35%, transparent); background: color-mix(in srgb, var(--ok) 7%, var(--surface)); }
.callout.warn { border-color: color-mix(in srgb, var(--accent-3) 40%, transparent); background: color-mix(in srgb, var(--accent-3) 8%, var(--surface)); }
.callout.real { border-color: color-mix(in srgb, var(--accent-2) 40%, transparent); background: color-mix(in srgb, var(--accent-2) 8%, var(--surface)); }
.callout p { margin: 0; }
.formula {
  display: inline-block; font-family: var(--font-mono); font-weight: 600; font-size: 1.15rem;
  padding: 10px 18px; border-radius: 12px; background: var(--surface-2); border: 1px solid var(--border); color: var(--text);
}
.formula-row { display: flex; flex-wrap: wrap; gap: 12px; margin: 14px 0; }
.gl { border-bottom: 1.5px dashed var(--accent); cursor: help; color: inherit; }
.gl-tip {
  position: absolute; z-index: 300; max-width: 280px; padding: 12px 14px; border-radius: 12px;
  background: var(--surface); border: 1px solid var(--border-strong); box-shadow: var(--shadow-lg);
  font-size: .88rem; color: var(--text-2); pointer-events: none;
}
.gl-tip b { display: block; color: var(--text); font-family: var(--font-head); margin-bottom: 3px; }
.tryit { list-style: none; padding: 0; margin: 14px 0 0; display: grid; gap: 8px; }
.tryit li { padding: 10px 14px; border-radius: 12px; background: var(--surface); border: 1px dashed var(--border-strong); font-size: .94rem; color: var(--text-2); }
.tryit li::before { content: "▶ "; color: var(--accent); font-size: .75rem; }

.example { border-radius: var(--radius); border: 1px solid var(--border); background: var(--surface); overflow: hidden; }
.example .prob { padding: 20px 22px; border-bottom: 1px solid var(--border); background: var(--surface-2); }
.example .prob b { font-family: var(--font-head); }
.example ol { list-style: none; counter-reset: s; margin: 0; padding: 14px 22px 20px; }
.example ol li { counter-increment: s; padding: 10px 0 10px 40px; position: relative; border-bottom: 1px dashed var(--border); animation: fadeUp .45s ease both; }
.example ol li::before { content: counter(s); position: absolute; left: 0; top: 10px; width: 26px; height: 26px; border-radius: 50%; display: grid; place-items: center; font-size: .78rem; font-weight: 700; background: var(--tc, var(--accent)); color: #fff; }
.example .actions { padding: 0 22px 20px; display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.example .ans { padding: 14px 22px; background: color-mix(in srgb, var(--ok) 10%, transparent); border-top: 1px solid var(--border); font-weight: 600; }
@keyframes fadeUp { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

.summary-card { border-radius: var(--radius-lg); padding: 28px; background: var(--surface); border: 1px solid var(--border); position: relative; overflow: hidden; }
.summary-card::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 4px; background: var(--grad); }
.summary-card ul { padding-left: 20px; }
.lesson-nav { display: flex; justify-content: space-between; gap: 14px; flex-wrap: wrap; margin-top: 40px; padding-top: 28px; border-top: 1px solid var(--border); }
.lesson-nav a { flex: 1 1 240px; padding: 16px 20px; border-radius: 14px; border: 1px solid var(--border); background: var(--surface); color: var(--text); }
.lesson-nav a:hover { text-decoration: none; border-color: var(--accent); }
.lesson-nav a small { display: block; color: var(--muted); font-size: .78rem; }
.lesson-nav a.next { text-align: right; }
.complete-bar { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; padding: 20px 24px; border-radius: var(--radius); background: var(--grad-soft); border: 1px solid var(--border); margin-top: 26px; }

/* ---------- Simulator frame ---------- */
.sim {
  border-radius: var(--radius); border: 1px solid var(--border); background: var(--surface);
  overflow: hidden; box-shadow: var(--shadow); margin: 18px 0;
}
.sim-head { display: flex; align-items: center; gap: 12px; padding: 12px 16px; border-bottom: 1px solid var(--border); background: var(--surface-2); }
.sim-head h4 { margin: 0; font-size: .98rem; flex: 1; }
.sim-badge { font-family: var(--font-mono); font-size: .66rem; font-weight: 700; letter-spacing: .12em; padding: 3px 9px; border-radius: 999px; color: var(--ok); background: color-mix(in srgb, var(--ok) 12%, transparent); display: inline-flex; gap: 6px; align-items: center; }
.sim-badge::before { content: ""; width: 6px; height: 6px; border-radius: 50%; background: var(--ok); animation: pulse 1.6s infinite; }
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: .2; } }
.sim-body { display: grid; grid-template-columns: minmax(0, 1fr) 250px; }
.sim.compact .sim-body, .sim.wide .sim-body { grid-template-columns: 1fr; }
.sim-stage { position: relative; background: var(--sim-bg); min-height: 200px; display: grid; place-items: center; padding: 10px;
  background-image: linear-gradient(var(--sim-grid) 1px, transparent 1px), linear-gradient(90deg, var(--sim-grid) 1px, transparent 1px); background-size: 24px 24px; }
.sim-stage svg, .sim-stage canvas { width: 100%; height: auto; }
.sim-controls { padding: 16px; border-left: 1px solid var(--border); display: flex; flex-direction: column; gap: 16px; }
.sim.compact .sim-controls:empty, .sim-controls:empty { display: none; }
.sim.compact .sim-controls, .sim.wide .sim-controls { border-left: none; border-top: 1px solid var(--border); flex-direction: row; flex-wrap: wrap; }
.sim.compact .sim-controls > *, .sim.wide .sim-controls > * { flex: 1 1 200px; }
@media (max-width: 760px) {
  .sim-body { grid-template-columns: 1fr; }
  .sim-controls { border-left: none; border-top: 1px solid var(--border); }
}
.ctl label { display: flex; justify-content: space-between; font-size: .82rem; font-weight: 600; color: var(--text-2); margin-bottom: 6px; }
.ctl label output { font-family: var(--font-mono); color: var(--accent); }
input[type="range"] { -webkit-appearance: none; appearance: none; width: 100%; height: 6px; border-radius: 6px; background: var(--surface-2); border: 1px solid var(--border); outline-offset: 4px; }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 18px; height: 18px; border-radius: 50%; background: var(--grad); border: 2px solid #fff; box-shadow: 0 2px 8px rgba(0,0,0,.3); cursor: grab; }
input[type="range"]::-moz-range-thumb { width: 16px; height: 16px; border-radius: 50%; background: var(--accent); border: 2px solid #fff; cursor: grab; }
.seg { display: flex; flex-wrap: wrap; gap: 4px; padding: 4px; border-radius: 12px; background: var(--surface-2); border: 1px solid var(--border); }
.seg button { flex: 1 1 auto; padding: 7px 10px; border: none; border-radius: 9px; background: transparent; color: var(--text-2); font: 600 .8rem var(--font-body); cursor: pointer; }
.seg button.on { background: var(--surface); color: var(--accent); box-shadow: var(--shadow-sm); }
.switch { display: flex; align-items: center; justify-content: space-between; gap: 10px; font-size: .86rem; font-weight: 600; color: var(--text-2); cursor: pointer; }
.switch input { display: none; }
.switch .tr { width: 44px; height: 24px; border-radius: 99px; background: var(--lo); position: relative; transition: background .2s; flex: none; }
.switch .tr::after { content: ""; position: absolute; width: 18px; height: 18px; border-radius: 50%; background: #fff; top: 3px; left: 3px; transition: transform .2s; box-shadow: 0 1px 4px rgba(0,0,0,.3); }
.switch input:checked + .tr { background: var(--ok); }
.switch input:checked + .tr::after { transform: translateX(20px); }
.ctl select { width: 100%; padding: 8px 10px; border-radius: 10px; border: 1px solid var(--border); background: var(--surface-2); color: var(--text); font: 500 .9rem var(--font-body); }
.sim-readouts { display: flex; flex-wrap: wrap; gap: 0; border-top: 1px solid var(--border); }
.sim-readouts:empty { display: none; }
.ro { flex: 1 1 120px; padding: 10px 16px; border-right: 1px solid var(--border); }
.ro:last-child { border-right: none; }
.ro span { display: block; font-size: .7rem; text-transform: uppercase; letter-spacing: .1em; color: var(--muted); font-weight: 600; }
.ro b { font-family: var(--font-mono); font-size: 1.05rem; color: var(--ro, var(--text)); }
.sim-note { padding: 10px 16px; font-size: .88rem; color: var(--text-2); border-top: 1px solid var(--border); background: var(--surface-2); }
.sim-note:empty { display: none; }
.sim-eq { font-family: var(--font-mono); font-size: .95rem; }

/* SVG simulator classes */
.s-wire { fill: none; stroke: var(--wire); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
.s-thin { fill: none; stroke: var(--wire); stroke-width: 2; }
.s-cut { fill: var(--sim-bg); stroke: none; }
.s-text { fill: var(--text); font-family: var(--font-mono); font-size: 13px; font-weight: 600; }
.s-label { fill: var(--muted); font-family: var(--font-body); font-size: 12px; font-weight: 600; }
.s-big { fill: var(--text); font-family: var(--font-head); font-size: 18px; font-weight: 700; }
.s-acc { stroke: var(--accent); }
.s-fill-acc { fill: var(--accent); }
.s-electron { fill: var(--electron); }
.s-conv { fill: var(--conv); }
.s-axis { stroke: var(--muted); stroke-width: 1.2; fill: none; }
.s-gridline { stroke: var(--sim-grid); stroke-width: 1; }

/* ---------- Quiz ---------- */
.quiz { display: grid; gap: 18px; }
.q { padding: 22px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--border); }
.q-head { display: flex; gap: 10px; align-items: baseline; margin-bottom: 14px; }
.q-head .qn { font-family: var(--font-mono); font-weight: 700; color: var(--accent); font-size: .85rem; flex: none; }
.q-head p { margin: 0; font-weight: 600; color: var(--text); font-size: 1.02rem; }
.opts { display: grid; gap: 9px; }
.opt { text-align: left; padding: 12px 15px; border-radius: 12px; border: 1.5px solid var(--border); background: var(--surface-2); color: var(--text); font: 500 .95rem var(--font-body); cursor: pointer; display: flex; gap: 11px; align-items: center; transition: border-color .15s, transform .15s; }
.opt:hover:not([disabled]) { border-color: var(--accent); transform: translateX(3px); }
.opt .k { flex: none; width: 26px; height: 26px; border-radius: 8px; display: grid; place-items: center; font-family: var(--font-mono); font-size: .78rem; font-weight: 700; background: var(--surface); border: 1px solid var(--border); }
.opt.sel { border-color: var(--accent); }
.opt.correct { border-color: var(--ok); background: color-mix(in srgb, var(--ok) 12%, var(--surface)); }
.opt.correct .k { background: var(--ok); color: #fff; border-color: var(--ok); }
.opt.wrong { border-color: var(--danger); background: color-mix(in srgb, var(--danger) 10%, var(--surface)); }
.opt.wrong .k { background: var(--danger); color: #fff; border-color: var(--danger); }
.opt[disabled] { cursor: default; }
.num-ans { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.num-ans input { width: 160px; padding: 11px 14px; border-radius: 12px; border: 1.5px solid var(--border); background: var(--surface-2); color: var(--text); font: 600 1rem var(--font-mono); }
.num-ans input:focus { border-color: var(--accent); outline: none; }
.num-ans .unit { font-family: var(--font-mono); color: var(--muted); }
.feedback { margin-top: 14px; padding: 12px 15px; border-radius: 12px; font-size: .93rem; animation: fadeUp .3s ease; }
.feedback.ok { background: color-mix(in srgb, var(--ok) 12%, transparent); color: var(--text); border: 1px solid color-mix(in srgb, var(--ok) 35%, transparent); }
.feedback.bad { background: color-mix(in srgb, var(--danger) 10%, transparent); color: var(--text); border: 1px solid color-mix(in srgb, var(--danger) 30%, transparent); }
.quiz-score { display: flex; align-items: center; gap: 18px; padding: 20px 24px; border-radius: var(--radius); background: var(--grad-soft); border: 1px solid var(--border); flex-wrap: wrap; }
.quiz-score .big { font-family: var(--font-head); font-size: 2.2rem; font-weight: 700; }

/* ---------- Challenge ---------- */
.challenge { border-radius: var(--radius-lg); border: 1.5px solid color-mix(in srgb, var(--accent-3) 45%, transparent); background: color-mix(in srgb, var(--accent-3) 6%, var(--surface)); padding: 22px; }
.challenge .ch-head { display: flex; gap: 12px; align-items: center; margin-bottom: 10px; }
.challenge .ch-head .ic { font-size: 1.6rem; }
.challenge .ch-actions { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 12px; }

/* ---------- Exam ---------- */
.exam-shell { max-width: 860px; margin: 0 auto; }
.exam-top { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; margin-bottom: 18px; }
.timer { font-family: var(--font-mono); font-weight: 700; font-size: 1.15rem; padding: 8px 16px; border-radius: 12px; background: var(--surface); border: 1px solid var(--border); }
.timer.low { color: var(--danger); border-color: var(--danger); animation: pulse 1s infinite; }
.exam-dots { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 18px; }
.exam-dots button { width: 32px; height: 32px; border-radius: 9px; border: 1px solid var(--border); background: var(--surface); color: var(--text-2); font: 600 .8rem var(--font-mono); cursor: pointer; }
.exam-dots button.ans { background: color-mix(in srgb, var(--accent) 16%, var(--surface)); border-color: var(--accent); color: var(--text); }
.exam-dots button.cur { outline: 2px solid var(--accent-2); outline-offset: 2px; }
.bar { height: 10px; border-radius: 10px; background: var(--surface-2); overflow: hidden; border: 1px solid var(--border); }
.bar i { display: block; height: 100%; background: var(--grad); border-radius: 10px; transition: width .8s ease; }
.breakdown { display: grid; gap: 12px; }
.breakdown .row { display: grid; grid-template-columns: 1fr 140px 60px; gap: 14px; align-items: center; font-size: .92rem; }
@media (max-width: 560px) { .breakdown .row { grid-template-columns: 1fr 80px 50px; } }

/* ---------- Progress / badges ---------- */
.stat { padding: 22px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--border); }
.stat b { display: block; font-family: var(--font-head); font-size: 2rem; }
.stat span { color: var(--muted); font-size: .88rem; }
.badges { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 14px; }
.badge { text-align: center; padding: 20px 12px; border-radius: var(--radius); background: var(--surface); border: 1px solid var(--border); }
.badge .em { font-size: 2.2rem; display: block; margin-bottom: 6px; }
.badge.locked { opacity: .45; filter: grayscale(1); }
.badge b { display: block; font-family: var(--font-head); font-size: .95rem; }
.badge small { color: var(--muted); font-size: .78rem; }

/* ---------- Lab ---------- */
.lab-wrap { display: grid; grid-template-columns: 270px minmax(0, 1fr); gap: 28px; padding-top: 36px; padding-bottom: 60px; }
.lab-list { position: sticky; top: 88px; align-self: start; max-height: calc(100vh - 110px); overflow: auto; }
.lab-list button { width: 100%; text-align: left; padding: 10px 12px; border-radius: 10px; border: none; background: transparent; color: var(--text-2); font: 500 .9rem var(--font-body); cursor: pointer; display: flex; gap: 10px; align-items: center; }
.lab-list button:hover { background: var(--surface-2); }
.lab-list button.on { background: color-mix(in srgb, var(--accent) 12%, transparent); color: var(--text); font-weight: 600; }
.lab-list h4 { font-size: .74rem; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); margin: 16px 12px 6px; }
@media (max-width: 900px) { .lab-wrap { grid-template-columns: 1fr; } .lab-list { position: static; max-height: 260px; border: 1px solid var(--border); border-radius: 14px; padding: 6px; } }

/* ---------- Glossary ---------- */
.search { width: 100%; padding: 15px 20px; border-radius: 14px; border: 1.5px solid var(--border); background: var(--surface); color: var(--text); font: 500 1rem var(--font-body); }
.search:focus { border-color: var(--accent); outline: none; box-shadow: var(--glow); }
.gloss-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 14px; margin-top: 24px; }
.gloss-item { padding: 18px 20px; border-radius: 14px; background: var(--surface); border: 1px solid var(--border); }
.gloss-item h4 { margin-bottom: 4px; }
.gloss-item p { margin: 0; font-size: .92rem; }
.gloss-item .tag { font-family: var(--font-mono); font-size: .7rem; color: var(--accent); }

/* ---------- Certificate ---------- */
.cert-form { display: grid; gap: 14px; max-width: 520px; }
.field label { display: block; font-weight: 600; font-size: .88rem; margin-bottom: 6px; }
.field input, .field select { width: 100%; padding: 12px 14px; border-radius: 12px; border: 1.5px solid var(--border); background: var(--surface); color: var(--text); font: 500 1rem var(--font-body); }
.cert-preview { border-radius: var(--radius); overflow: hidden; border: 1px solid var(--border); box-shadow: var(--shadow-lg); background: #fff; }
.cert-preview canvas { width: 100%; height: auto; }

/* ---------- Toast ---------- */
.toasts { position: fixed; right: 18px; bottom: 18px; z-index: 500; display: grid; gap: 10px; }
.toast { display: flex; gap: 12px; align-items: center; padding: 13px 18px; border-radius: 14px; background: var(--surface); border: 1px solid var(--border-strong); box-shadow: var(--shadow-lg); font-weight: 600; font-size: .92rem; animation: toastIn .35s cubic-bezier(.2,1.4,.5,1); max-width: 340px; }
.toast .em { font-size: 1.4rem; }
.toast small { display: block; font-weight: 500; color: var(--muted); }
@keyframes toastIn { from { opacity: 0; transform: translateY(20px) scale(.95); } }

/* ---------- Reveal on scroll ---------- */
.reveal { opacity: 0; transform: translateY(24px); transition: opacity .7s ease, transform .7s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ---------- Misc ---------- */
.cta-band { border-radius: var(--radius-lg); padding: clamp(32px, 5vw, 60px); background: var(--grad); color: #fff; position: relative; overflow: hidden; text-align: center; }
.cta-band h2, .cta-band p { color: #fff; }
.cta-band .btn { background: #fff; color: #1d1650; border: none; }
.marquee { overflow: hidden; border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); background: var(--surface); padding: 16px 0; }
.marquee-track { display: flex; gap: 46px; width: max-content; animation: marq 40s linear infinite; font-family: var(--font-head); font-weight: 600; color: var(--muted); white-space: nowrap; }
.marquee-track span::before { content: "⚡ "; color: var(--accent); }
@keyframes marq { to { transform: translateX(-50%); } }
.kbd-row { display: flex; gap: 8px; flex-wrap: wrap; }
table.tt { border-collapse: collapse; font-family: var(--font-mono); font-size: .9rem; margin: 10px 0; }
table.tt th, table.tt td { border: 1px solid var(--border); padding: 6px 14px; text-align: center; }
table.tt th { background: var(--surface-2); }
table.tt tr.on td { background: color-mix(in srgb, var(--accent) 18%, transparent); color: var(--text); font-weight: 700; }
pre.code { margin: 0; padding: 14px 0; font-family: var(--font-mono); font-size: .82rem; line-height: 1.6; background: #0b1024; color: #cfd8ff; border-radius: 12px; overflow: auto; }
pre.code .ln { display: block; padding: 0 14px; border-left: 3px solid transparent; }
pre.code .ln.on { background: rgba(34, 211, 238, .14); border-left-color: #22d3ee; color: #fff; }
pre.code .cm { color: #6b7bb5; }
pre.code .kw { color: #c792ea; }
pre.code .fn { color: #82aaff; }
pre.code .nu { color: #f78c6c; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; scroll-behavior: auto !important; }
  .reveal { opacity: 1; transform: none; }
}
@media print {
  .site-header, .site-footer, .lesson-side, .sim, .lesson-nav, .complete-bar, .toasts { display: none !important; }
  body { background: #fff; color: #000; }
}

/* MasteryLeap wordmark */
.brand b.leap { font-weight: 700; background: var(--grad); -webkit-background-clip: text; background-clip: text; color: transparent; }