/* ============================================================
   SAT Math Lab — page styles
   Design language: ink navy + paper white + pencil yellow (site
   brand), with two lab accents: slope orange and data green.
   Interactive panels sit on millimeter graph paper.
   ============================================================ */

:root {
  --ml-ink: #14264C;
  --ml-paper: #FBFAF6;
  --ml-pencil: #F5B91E;
  --ml-slope: #E8590C;   /* rise/run, roots, line B */
  --ml-data: #2F9E44;    /* vertices, best fit, sin leg */
  --ml-blue: #3B5BDB;    /* secondary line */
  --ml-mist: #D9DEEA;
  --ml-rule: rgba(20, 38, 76, 0.12);
  --ml-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

.ml-main { background: var(--ml-paper); color: var(--ml-ink); font-family: 'Public Sans', system-ui, sans-serif; line-height: 1.6; }
.ml-main * { box-sizing: border-box; }

/* ---------- graph paper ---------- */
.ml-graphpaper {
  background-color: var(--ml-paper);
  background-image:
    linear-gradient(rgba(20,38,76,0.10) 1px, transparent 1px),
    linear-gradient(90deg, rgba(20,38,76,0.10) 1px, transparent 1px),
    linear-gradient(rgba(20,38,76,0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(20,38,76,0.05) 1px, transparent 1px);
  background-size: 40px 40px, 40px 40px, 8px 8px, 8px 8px;
}

/* ---------- hero ---------- */
.ml-hero {
  background: var(--ml-ink);
  color: #fff;
  padding: 56px 20px 64px;
  position: relative;
  overflow: hidden;
}
.ml-hero-wrap { max-width: 1200px; margin: 0 auto; display: grid; gap: 40px; align-items: center; }
@media (min-width: 960px) { .ml-hero-wrap { grid-template-columns: minmax(0,1fr) 480px; } }
.ml-hero-eyebrow {
  display: inline-block; font-size: .8rem; font-weight: 700;
  letter-spacing: .14em; text-transform: uppercase;
  color: var(--ml-pencil); margin-bottom: 18px;
}
.ml-hero h1 {
  font-family: 'Fraunces', Georgia, serif; font-weight: 650;
  font-size: clamp(2rem, 4.6vw, 3.2rem); line-height: 1.12; margin: 0; color: #fff;
}
.ml-hero-lead { margin: 20px 0 28px; max-width: 34em; color: var(--ml-mist); font-size: 1.06rem; }
.ml-hero-ctas { display: flex; gap: 14px; flex-wrap: wrap; }
.ml-btn {
  display: inline-block; text-decoration: none; font-weight: 700; cursor: pointer;
  padding: 13px 22px; border-radius: 8px; font-size: 1rem; border: none;
  transition: transform .12s ease;
  font-family: inherit;
}
.ml-btn:hover { transform: translateY(-1px); }
.ml-btn:focus-visible { outline: 3px solid var(--ml-pencil); outline-offset: 2px; }
.ml-btn-yellow { background: var(--ml-pencil); color: var(--ml-ink); }
.ml-btn-ghost { border: 2px solid rgba(255,255,255,.55); color: #fff; background: transparent; }
.ml-hero-stage {
  background: rgba(255,255,255,.04);
  border: 1px solid rgba(255,255,255,.16);
  border-radius: 16px; padding: 14px;
}
.ml-hero-stage svg { display: block; width: 100%; height: auto; }
.ml-hero-stage-bar { display: flex; align-items: center; justify-content: space-between; padding: 8px 6px 0; font-size: .8rem; color: var(--ml-mist); }
.ml-hero-stage-bar .ml-mono { color: var(--ml-pencil); }

/* ---------- section scaffolding ---------- */
.ml-section { padding: 64px 20px; }
.ml-section-ink { background: var(--ml-ink); color: #fff; }
.ml-wrap { max-width: 1200px; margin: 0 auto; }
.ml-kicker {
  font-size: .78rem; font-weight: 700; letter-spacing: .14em; text-transform: uppercase;
  margin-bottom: 10px; display: flex; align-items: center; gap: 10px;
}
.ml-kicker .ml-domain-tag { background: var(--ml-ink); color: var(--ml-pencil); border-radius: 4px; padding: 2px 8px; }
.ml-section-ink .ml-kicker .ml-domain-tag { background: var(--ml-pencil); color: var(--ml-ink); }
.ml-section h2 {
  font-family: 'Fraunces', Georgia, serif; font-weight: 650;
  font-size: clamp(1.5rem, 3vw, 2.1rem); line-height: 1.2; margin: 0 0 12px;
}
.ml-section-intro { max-width: 44em; margin: 0 0 28px; font-size: 1.02rem; }
.ml-section-ink .ml-section-intro { color: var(--ml-mist); }

/* sticky in-page nav */
.ml-subnav {
  position: sticky; top: 0; z-index: 40;
  background: var(--ml-paper);
  border-bottom: 1px solid var(--ml-rule);
  overflow-x: auto; -webkit-overflow-scrolling: touch;
}
.ml-subnav-inner { max-width: 1200px; margin: 0 auto; display: flex; gap: 4px; padding: 10px 16px; white-space: nowrap; }
.ml-subnav a {
  text-decoration: none; color: var(--ml-ink); font-size: .88rem; font-weight: 600;
  padding: 7px 13px; border-radius: 999px;
}
.ml-subnav a:hover { background: rgba(20,38,76,.08); }
.ml-subnav a.ml-subnav-cta { background: var(--ml-pencil); }

/* ---------- lab panels ---------- */
.ml-panel {
  display: grid; gap: 24px;
  background: #fff; border: 1px solid var(--ml-rule); border-radius: 16px;
  padding: 24px; box-shadow: 0 8px 24px rgba(20,38,76,.06);
}
@media (min-width: 900px) { .ml-panel { grid-template-columns: minmax(0,1.25fr) minmax(260px,1fr); align-items: start; } }
.ml-stage {
  border: 1px solid var(--ml-rule); border-radius: 12px; overflow: hidden;
  touch-action: none;
}
.ml-stage svg { display: block; width: 100%; height: auto; }
.ml-controls { display: flex; flex-direction: column; gap: 16px; }
.ml-control label { display: flex; justify-content: space-between; font-weight: 600; font-size: .92rem; margin-bottom: 6px; }
.ml-control label .ml-mono { font-weight: 700; }
.ml-control input[type="range"] { width: 100%; accent-color: var(--ml-ink); }
.ml-mono { font-family: var(--ml-mono); }
.ml-readout {
  background: var(--ml-ink); color: #fff; border-radius: 10px; padding: 14px 16px;
  font-family: var(--ml-mono); font-size: 1.02rem; line-height: 1.7;
  white-space: pre-line;
}
.ml-readout .hl-y { color: var(--ml-pencil); }
.ml-readout .hl-o { color: #FFA94D; }
.ml-readout .hl-g { color: #69DB7C; }
.ml-note {
  border-left: 4px solid var(--ml-pencil); background: rgba(245,185,30,.12);
  border-radius: 0 10px 10px 0; padding: 12px 16px; font-size: .95rem;
}
.ml-note strong { display: block; margin-bottom: 2px; }
.ml-chiprow { display: flex; gap: 8px; flex-wrap: wrap; }
.ml-chip {
  border: 1.5px solid var(--ml-ink); background: #fff; color: var(--ml-ink);
  border-radius: 999px; padding: 7px 14px; font-size: .88rem; font-weight: 600;
  cursor: pointer; font-family: inherit;
}
.ml-chip[aria-pressed="true"] { background: var(--ml-ink); color: #fff; }
.ml-chip:focus-visible { outline: 3px solid var(--ml-pencil); outline-offset: 2px; }

/* drag handles */
.ml-handle { cursor: grab; }
.ml-handle:active { cursor: grabbing; }
.ml-handle:focus { outline: none; }
.ml-handle:focus-visible { stroke: var(--ml-pencil); stroke-width: 4; }

/* flash animation when something snaps/solves */
@keyframes ml-flash { 0% { opacity: 0; r: 26; } 40% { opacity: .9; } 100% { opacity: 0; r: 6; } }
.ml-flash { animation: ml-flash .7s ease-out forwards; transform-origin: center; }

/* ---------- term popovers ---------- */
.term {
  border-bottom: 2px dotted var(--ml-slope); cursor: help; position: relative;
  text-decoration: none; color: inherit;
}
.ml-pop {
  position: absolute; z-index: 60; max-width: 280px;
  background: var(--ml-ink); color: #fff; border-radius: 10px; padding: 12px 14px;
  font-size: .86rem; line-height: 1.5; box-shadow: 0 10px 30px rgba(20,38,76,.35);
  pointer-events: none;
}
.ml-pop strong { color: var(--ml-pencil); display: block; margin-bottom: 3px; }

/* ---------- worked examples ---------- */
.ml-steps { background: #fff; border: 1px solid var(--ml-rule); border-radius: 16px; padding: 24px; }
.ml-steps h3 { font-family: 'Fraunces', Georgia, serif; margin: 0 0 4px; font-size: 1.2rem; }
.ml-steps-problem { font-size: .95rem; margin: 0 0 16px; color: rgba(20,38,76,.8); }
.ml-step {
  display: none; gap: 12px; align-items: baseline;
  padding: 10px 0; border-top: 1px dashed var(--ml-rule);
}
.ml-step.shown { display: flex; }
.ml-step-num {
  flex: none; width: 26px; height: 26px; border-radius: 50%;
  background: var(--ml-pencil); color: var(--ml-ink); font-weight: 700; font-size: .82rem;
  display: inline-flex; align-items: center; justify-content: center;
  transform: translateY(4px);
}
.ml-step .ml-mono { font-size: 1.05rem; }
.ml-step-why { font-size: .88rem; color: rgba(20,38,76,.72); }
.ml-steps-bar { display: flex; align-items: center; gap: 14px; margin-top: 16px; }
.ml-steps-dots { display: flex; gap: 6px; }
.ml-steps-dots span { width: 8px; height: 8px; border-radius: 50%; background: var(--ml-rule); }
.ml-steps-dots span.on { background: var(--ml-ink); }
.ml-steps-hintkey { font-size: .82rem; color: rgba(20,38,76,.6); }

/* ---------- practice arena ---------- */
.ml-arena { display: grid; gap: 24px; }
@media (min-width: 980px) { .ml-arena { grid-template-columns: 250px minmax(0,1fr); align-items: start; } }
.ml-arena-side {
  background: rgba(255,255,255,.05); border: 1px solid rgba(255,255,255,.16);
  border-radius: 16px; padding: 20px; display: flex; flex-direction: column; gap: 18px;
}
@media (min-width: 980px) { .ml-arena-side { position: sticky; top: 64px; } }
.ml-arena-side h3 { margin: 0; font-size: .8rem; letter-spacing: .12em; text-transform: uppercase; color: var(--ml-mist); }
.ml-arena .ml-chip { border-color: rgba(255,255,255,.5); background: transparent; color: #fff; }
.ml-arena .ml-chip[aria-pressed="true"] { background: var(--ml-pencil); border-color: var(--ml-pencil); color: var(--ml-ink); }
.ml-scorebox { font-family: var(--ml-mono); font-size: .95rem; line-height: 1.8; color: var(--ml-mist); }
.ml-scorebox b { color: var(--ml-pencil); font-size: 1.3rem; }
.ml-qmap { display: grid; grid-template-columns: repeat(auto-fill, minmax(26px, 1fr)); gap: 5px; }
.ml-qmap button {
  aspect-ratio: 1; border-radius: 6px; border: 1px solid rgba(255,255,255,.35);
  background: transparent; color: #fff; font-size: .68rem; font-weight: 600; cursor: pointer;
  font-family: var(--ml-mono); padding: 0;
}
.ml-qmap button.cur { outline: 2px solid var(--ml-pencil); outline-offset: 1px; }
.ml-qmap button.ok { background: var(--ml-data); border-color: var(--ml-data); }
.ml-qmap button.bad { background: var(--ml-slope); border-color: var(--ml-slope); }

.ml-qcard {
  background: var(--ml-paper); color: var(--ml-ink);
  border-radius: 16px; padding: 28px; min-height: 420px;
  display: flex; flex-direction: column; gap: 18px;
}
.ml-qmeta { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; font-size: .78rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.ml-qmeta .tag { background: var(--ml-ink); color: #fff; border-radius: 4px; padding: 3px 9px; }
.ml-qmeta .tag.diff-1 { background: var(--ml-data); }
.ml-qmeta .tag.diff-2 { background: var(--ml-pencil); color: var(--ml-ink); }
.ml-qmeta .tag.diff-3 { background: var(--ml-slope); }
.ml-qtext { font-size: 1.1rem; line-height: 1.65; font-family: Georgia, 'Times New Roman', serif; }
.ml-qtext .ml-mono { font-size: 1.02em; }
.ml-choices { display: grid; gap: 10px; }
.ml-choice {
  display: flex; gap: 12px; align-items: baseline; text-align: left;
  border: 1.5px solid var(--ml-rule); border-radius: 10px; background: #fff;
  padding: 12px 16px; font-size: 1rem; cursor: pointer; font-family: Georgia, serif;
  transition: border-color .1s ease;
}
.ml-choice:hover { border-color: var(--ml-ink); }
.ml-choice:focus-visible { outline: 3px solid var(--ml-pencil); outline-offset: 1px; }
.ml-choice .key {
  flex: none; width: 26px; height: 26px; border-radius: 50%; border: 1.5px solid var(--ml-ink);
  display: inline-flex; align-items: center; justify-content: center;
  font-family: 'Public Sans', sans-serif; font-weight: 700; font-size: .8rem;
  transform: translateY(4px);
}
.ml-choice.sel { border-color: var(--ml-ink); box-shadow: inset 0 0 0 1px var(--ml-ink); }
.ml-choice.sel .key { background: var(--ml-ink); color: #fff; }
.ml-choice.right { border-color: var(--ml-data); box-shadow: inset 0 0 0 1px var(--ml-data); background: rgba(47,158,68,.07); }
.ml-choice.right .key { background: var(--ml-data); border-color: var(--ml-data); color: #fff; }
.ml-choice.wrong { border-color: var(--ml-slope); box-shadow: inset 0 0 0 1px var(--ml-slope); background: rgba(232,89,12,.06); }
.ml-choice.wrong .key { background: var(--ml-slope); border-color: var(--ml-slope); color: #fff; }
.ml-gridin { display: flex; gap: 10px; align-items: center; }
.ml-gridin input {
  font-family: var(--ml-mono); font-size: 1.2rem; padding: 10px 14px; width: 170px;
  border: 1.5px solid var(--ml-ink); border-radius: 10px; background: #fff; color: var(--ml-ink);
}
.ml-gridin input:focus-visible { outline: 3px solid var(--ml-pencil); outline-offset: 1px; }
.ml-qactions { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: auto; }
.ml-btn-line { background: transparent; border: 2px solid var(--ml-ink); color: var(--ml-ink); padding: 11px 20px; }
.ml-hint, .ml-expl {
  border-radius: 10px; padding: 14px 16px; font-size: .96rem; line-height: 1.6;
}
.ml-hint { background: rgba(59,91,219,.08); border-left: 4px solid var(--ml-blue); }
.ml-expl { background: rgba(47,158,68,.08); border-left: 4px solid var(--ml-data); }
.ml-expl.was-wrong { background: rgba(232,89,12,.07); border-left-color: var(--ml-slope); }
.ml-expl strong, .ml-hint strong { display: block; margin-bottom: 4px; }
.ml-verdict { font-weight: 700; font-size: 1.02rem; }
.ml-verdict.ok { color: var(--ml-data); }
.ml-verdict.bad { color: var(--ml-slope); }
[hidden] { display: none !important; }

/* ---------- CTA strip ---------- */
.ml-cta-strip { background: var(--ml-pencil); color: var(--ml-ink); padding: 40px 20px; }
.ml-cta-strip .ml-wrap { display: flex; gap: 20px; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.ml-cta-strip h2 { font-family: 'Fraunces', Georgia, serif; margin: 0; font-size: 1.4rem; }
.ml-cta-strip p { margin: 4px 0 0; }
.ml-btn-ink { background: var(--ml-ink); color: #fff; }

@media (prefers-reduced-motion: reduce) {
  .ml-main * { animation: none !important; transition: none !important; }
}