/* ============================================================
   S3 Physics — shared stylesheet (hub + topic / beta pages)
   Mirrors the Higher Physics design system (glass panels, accent
   surfaces, gradient pill buttons, chevron reveals) but in the
   S3 TEAL palette. Only the colour tones differ from Higher.
   Token names alias both the hub (--accent/--text/--bg0…) and the
   topic pages (--phys-accent/--text-main/--bg-page…).
   Page-specific widget CSS stays inline on each page.
   ============================================================ */

/* ---------- GLOBAL FIX ---------- */
*, *::before, *::after { box-sizing: border-box; }
html, body { max-width: 100%; }
body { margin: 0; overflow-x: hidden; }
img, iframe { max-width: 100%; height: auto; display: block; }

/* ---------- A11Y HELPERS ---------- */
.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap; border: 0;
}
.skip-link {
  position: absolute;
  left: -999px; top: 10px;
  background: var(--accent);
  color: #00231c;
  padding: 0.6rem 0.9rem;
  border-radius: 12px;
  font-weight: 900;
  z-index: 1200;
  text-decoration: none;
  box-shadow: 0 12px 24px rgba(0,0,0,0.14);
}
.skip-link:focus { left: 10px; outline: 3px solid rgba(255,255,255,0.9); outline-offset: 3px; }

/* ============================================================
   THEME TOKENS — light mode defaults (teal identity)
   ============================================================ */
:root {
  --font-stack: "Trebuchet MS","Segoe UI",system-ui,-apple-system,sans-serif;

  --bg0:#f0fbf8;
  --bg1:#e7f6f1;
  --bg2:#ffffff;

  --text:#07221c;
  --muted:#356b5f;

  --accent:#00747c;
  /* hub-tile bands (assets/css/hub-tiles.css). White ink on all four:
     5.54 / 6.41 / 6.88 / 7.12 : 1. */
  --tile-1:#00747c; --tile-2:#0f6b5c; --tile-3:#2f5d8a; --tile-4:#6b4a86;
  --tile-ink:#ffffff;
  --accent-2:#00666b;
  --page-accent:var(--accent);
  --menu-accent:var(--accent);

  --cta-1:#00a9b2;
  --cta-2:#00666b;

  --card:#ffffff;
  --glass:rgba(255,255,255,0.86);
  --surface-2:rgba(0,138,145,0.06);

  --border:rgba(7,40,33,0.14);
  --border-soft:rgba(7,40,33,0.10);
  --border-accent:rgba(0,138,145,0.20);
  --border-strong:rgba(0,138,145,0.32);

  --shadow:0 18px 40px rgba(0,0,0,0.10);
  --shadow-soft:0 10px 22px rgba(0,0,0,0.08);
  --shadow-hover:0 18px 34px rgba(0,138,145,0.16);

  --tile-bg:rgba(255,255,255,0.92);
  --overlay-bg:rgba(255,255,255,0.82);
  --summary-bg:rgba(255,255,255,0.70);
  --footer-bg:rgba(255,255,255,0.80);

  --glow-1:rgba(0,138,145,0.14);
  --glow-2:rgba(0,190,200,0.10);

  --good:#15803d;
  --warm:#c2410c;
  --bad:var(--warm);

  --radius:18px;
  --radius-card:16px;
  --focus-ring:3px solid rgba(0,138,145,0.55);
  --focus-offset:4px;

  /* aliases used by S3 page markup */
  --phys-accent:var(--accent);
  --phys-accent-light:#3fd8e0;
  --phys-accent-dark:var(--accent-2);
  --bg-page:var(--bg0);
  --bg-card:var(--card);
  --bg-soft:var(--surface-2);
  --bg-soft-2:var(--surface-2);
  --text-main:var(--text);
  --text-muted:var(--muted);
  --line:var(--border);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg0:#08201a;
    --bg1:#0a241d;
    --bg2:#06150f;

    --text:#e6f5ef;
    --muted:#93c6b6;

    --accent:#2fd7e0;
    --accent-2:#a6f1f5;

    --cta-1:#13bec7;
    --cta-2:#0a777d;

    --card:#0f2a22;
    --glass:rgba(16,40,33,0.86);
    --surface-2:rgba(47,215,224,0.10);

    --border:rgba(255,255,255,0.16);
    --border-soft:rgba(255,255,255,0.10);
    --border-accent:rgba(47,215,224,0.30);
    --border-strong:rgba(47,215,224,0.42);

    --shadow:0 18px 40px rgba(0,0,0,0.50);
    --shadow-soft:0 10px 22px rgba(0,0,0,0.40);
    --shadow-hover:0 18px 34px rgba(47,215,224,0.22);

    --tile-bg:rgba(16,40,33,0.92);
    --overlay-bg:rgba(6,21,15,0.70);
    --summary-bg:rgba(16,40,33,0.66);
    --footer-bg:rgba(6,21,15,0.55);

    --glow-1:rgba(47,215,224,0.16);
    --glow-2:rgba(0,150,120,0.14);

    --good:#5dd693;
    --warm:#ff9d6e;

    --phys-accent-light:#7ff9ff;
    --focus-ring:3px solid rgba(47,215,224,0.70);
  }
}

/* ============================================================
   BASE
   ============================================================ */
body {
  font-family: var(--font-stack);
  color: var(--text);
  background:
    radial-gradient(900px 520px at 12% 0%, var(--glow-1), transparent 62%),
    radial-gradient(900px 520px at 88% 6%, var(--glow-2), transparent 58%),
    linear-gradient(180deg, var(--bg0), var(--bg1) 55%, var(--bg2) 100%);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}
:focus-visible { outline: var(--focus-ring); outline-offset: var(--focus-offset); }
a:focus-visible, button:focus-visible, select:focus-visible,
input:focus-visible, summary:focus-visible { outline: var(--focus-ring); outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}

/* ============================================================
   FLOATING BACK BUTTON (topic pages)
   ============================================================ */
.back-to-s3 {
  position: fixed;
  bottom: calc(20px + env(safe-area-inset-bottom));
  left: calc(20px + env(safe-area-inset-left));
  z-index: 300;
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  min-height: 44px;
  background: var(--card);
  padding: 0.6rem 1rem;
  border-radius: 12px;
  color: var(--text);
  font-weight: 900;
  text-decoration: none;
  font-size: 0.95rem;
  border: 1px solid var(--border-accent);
  box-shadow: var(--shadow-soft);
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
}
.back-to-s3:hover, .back-to-s3:focus-visible {
  transform: translateY(-1px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-hover);
}

/* ============================================================
   BANNER (Higher style)
   ============================================================ */
.banner-wrap {
  position: relative;
  width: 100%;
  overflow: hidden;
  flex-shrink: 0;
  box-shadow: 0 10px 24px rgba(0,0,0,0.12);
  z-index: 2;
  aspect-ratio: 3 / 1;
  background: var(--glass);
  border-bottom: 1px solid var(--border-soft);
}
.banner {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  opacity: 0;
  animation: fadeIn 1s ease forwards;
}
@keyframes fadeIn { to { opacity: 1; } }
.banner-tint {
  position: absolute;
  inset: 0;
  background: linear-gradient(120deg, rgba(0,138,145,0.18), rgba(0,190,200,0.10), rgba(255,255,255,0));
  mix-blend-mode: multiply;
  pointer-events: none;
  display: none;
}
.banner-overlay-text {
  position: absolute;
  bottom: 0; left: 0; right: 0;
  background: var(--overlay-bg);
  backdrop-filter: blur(12px) saturate(160%);
  -webkit-backdrop-filter: blur(12px) saturate(160%);
  border-top: 1px solid var(--border-soft);
  text-align: center;
  padding: 0.9rem 1rem;
}
/* Hub/landing pages: banner art already shows the title — hide the duplicate bar (SR-only) */
.banner-wrap.is-hub .banner-overlay-text {
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
  inset: auto;
  background: none;
  backdrop-filter: none;
  -webkit-backdrop-filter: none;
}
.banner-overlay-text h1 { margin: 0; font-size: 1.12rem; font-weight: 900; color: var(--text); }
.banner-overlay-text p { margin: 0.25rem 0 0; font-size: 0.95rem; color: var(--muted); font-weight: 800; }
@media (max-width: 560px) { .banner-overlay-text h1 { font-size: 1.02rem; } }

/* ============================================================
   MAIN LAYOUT + PANELS (glass, Higher style)
   ============================================================ */
.page-wrap {
  flex: 1;
  width: 100%;
  max-width: 1100px;
  margin: 1rem auto 2rem;
  padding: 0 12px 5rem;
}

.panel, .topic-box {
  background: var(--glass);
  border: 1px solid var(--border-soft);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-radius: var(--radius);
  padding: 1.2rem;
  box-shadow: var(--shadow-soft);
  margin: 0.95rem 0;
}
.topic-box { margin-bottom: 2rem; }
.panel.soft { background: var(--glass); }
.panel h2, .topic-box h2 {
  margin: 0 0 0.45rem;
  font-size: 1.18rem;
  font-weight: 900;
  letter-spacing: 0.2px;
  color: var(--text);
}
.panel p { margin: 0.35rem 0 0; line-height: 1.55; }
.topic-box a { color: var(--accent-2); font-weight: 900; text-decoration: none; }
.topic-box a:hover { text-decoration: underline; }
.muted { color: var(--muted); font-weight: 800; }
.page-intro { text-align: center; padding: 0.95rem 1rem; }
.page-intro p { margin: 0; font-weight: 900; color: var(--text); }

/* ---------- sticky sub-nav + deck cards (slides pages) ---------- */
.subnav-wrap {
  position: sticky; top: 0; z-index: 320;
  padding: calc(6px + env(safe-area-inset-top)) 10px 6px;
  background: var(--glass); backdrop-filter: blur(14px) saturate(170%); -webkit-backdrop-filter: blur(14px) saturate(170%);
  border-bottom: 1px solid var(--border-soft);
}
.subnav { display: flex; align-items: center; gap: 12px; padding: 8px 10px; border-radius: 16px; border: 1px solid var(--border-accent); background: var(--card); }
.subnav-links { display: flex; gap: 12px; flex-wrap: nowrap; overflow: auto; -webkit-overflow-scrolling: touch; scrollbar-width: none; flex: 1; min-width: 0; }
.subnav-links::-webkit-scrollbar { display: none; }
.subnav-link { display: inline-flex; align-items: center; min-height: 44px; text-decoration: none; font-weight: 900; color: var(--text); padding: 8px 4px; border-bottom: 3px solid transparent; white-space: nowrap; opacity: 0.95; font-size: 1rem; }
.subnav-link:hover { opacity: 1; border-bottom-color: var(--accent); }
.subnav-cta { flex-shrink: 0; display: inline-flex; align-items: center; gap: .35rem; padding: 7px 14px; min-height: 40px; border-radius: 10px; background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #fff; font-weight: 900; font-size: .95rem; text-decoration: none; white-space: nowrap; box-shadow: 0 6px 16px rgba(0,116,124,0.35); }

.backlink{display:inline-flex;align-items:center;gap:.4rem;min-height:44px;font-weight:900;color:var(--accent-2);text-decoration:none;margin:6px 0 .3rem}
.unit-note{margin:.15rem 0 0;font-weight:800;color:var(--muted);font-size:.9rem;line-height:1.5}
.deck-list{display:grid;gap:12px;margin-top:.85rem;grid-template-columns:repeat(auto-fit,minmax(min(280px,100%),1fr))}
.deck-card{display:flex;align-items:center;gap:.8rem;padding:.75rem .9rem;min-height:74px;
  border-radius:14px;border:1px solid var(--border);border-left:5px solid var(--accent);
  background:var(--card);color:var(--text);text-decoration:none;
  -webkit-tap-highlight-color:transparent;touch-action:manipulation;
  transition:transform .15s ease,border-color .15s ease,box-shadow .15s ease}
a.deck-card:hover,a.deck-card:focus-visible{transform:translateY(-1px);border-color:var(--border-accent);box-shadow:var(--shadow)}
.deck-card .deck-txt{display:flex;flex-direction:column;gap:.12rem;min-width:0;flex:1}
.deck-name{font-weight:900;line-height:1.22}
.deck-meta{font-weight:800;font-size:.78rem;color:var(--muted);letter-spacing:.01em}
.deck-card .go{color:var(--accent-2);font-weight:900;flex-shrink:0}
.deck-card.soon{background:var(--surface-2);color:var(--muted);
  border-style:dashed;border-left-style:solid;border-color:var(--border-soft);border-left-color:var(--border)}
.deck-card.soon .deck-ic{opacity:.45}
.deck-ic{width:44px;height:44px;flex-shrink:0;display:block}

/* section dividers (topic pages) */
.section-head { margin: 1.7rem 0 0.4rem; padding-top: 1.05rem; border-top: 1px solid var(--border-soft); }
.section-head:first-of-type { border-top: 0; padding-top: 0; }
.section-sub { margin: 0 0 0.8rem; color: var(--muted); font-weight: 800; }

/* accent inner surfaces */
.info-card, .core-revision-box, .checklist-box {
  background: var(--surface-2);
  border: 1px solid var(--border-accent);
  border-radius: 14px;
  padding: 1rem 1.1rem;
  margin: 0.75rem 0 1.1rem;
}
.core-grid { display: grid; gap: 0.75rem; }
@media (min-width: 700px) { .core-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.core-item-title { font-weight: 900; color: var(--text); }
.checklist-box ul { list-style: none; padding-left: 0; margin: 0.3rem 0; }
.checklist-box li::before { content: "☐ "; }

/* ============================================================
   COLLAPSIBLES (Higher details.mini style)
   ============================================================ */
.collapsible-panel { margin-top: 0.8rem; }
.collapsible-panel details {
  border-radius: 16px;
  border: 1px solid var(--border-accent);
  background: var(--surface-2);
  overflow: hidden;
  box-shadow: var(--shadow-soft);
}
.collapsible-panel summary {
  list-style: none;
  cursor: pointer;
  padding: 0.95rem 1rem;
  font-weight: 900;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 0.55rem;
  background: var(--summary-bg);
  border-bottom: 1px solid var(--border-soft);
}
.collapsible-panel summary::after {
  content: "▾";
  margin-left: auto;
  font-weight: 900;
  opacity: .8;
  transition: transform .18s ease;
}
.collapsible-panel details[open] summary::after { transform: rotate(180deg); }
details summary::-webkit-details-marker { display: none; }
.summary-icon { font-size: 1.2rem; }
.summary-text { flex: 1; }

/* dyslexia-friendly spacing inside open panels */
.collapsible-panel details ul { line-height: 1.75; margin-top: 0.8rem; margin-bottom: 0.8rem; }
.collapsible-panel details ul li { margin-bottom: 0.85rem; padding-left: 0.2rem; }
.collapsible-panel details ul li ul li { margin-bottom: 0.65rem; padding-left: 1rem; }
.collapsible-panel details h3 { margin-top: 1.1rem; margin-bottom: 0.6rem; }

/* ============================================================
   LEARN-FLOW STEP LABELS
   ============================================================ */
.step-label {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 900;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 0.2rem 0.7rem;
  border-radius: 999px;
  background: var(--accent);
  color: #fff;
  margin: 1rem 0 0.3rem;
}
.step-label.try   { background: #b8860b; color: #fff; }
.step-label.check { background: #2b59ff; color: #fff; }
@media (prefers-color-scheme: dark) {
  .step-label { color: #042019; }
  .step-label.try   { background: #ffca6f; color: #1b1b1b; }
  .step-label.check { background: #5fa0ff; color: #08121f; }
}

/* ============================================================
   CIRCUIT SYMBOL GALLERY
   ============================================================ */
.symbol-grid {
  display: grid;
  gap: 0.7rem;
  grid-template-columns: repeat(auto-fill, minmax(135px, 1fr));
  margin: 0.6rem 0 0.4rem;
}
.symbol-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.35rem;
  background: var(--card);
  border: 1px solid var(--border-soft);
  border-radius: 12px;
  padding: 0.7rem 0.55rem 0.8rem;
  text-align: center;
}
.ckt-symbol { width: 96px; height: 58px; color: var(--text); }
.sym-name { font-weight: 900; font-size: 0.95rem; }
.sym-fn { font-size: 0.82rem; color: var(--muted); line-height: 1.35; font-weight: 700; }

/* ============================================================
   WORKED EXAMPLES & TABLES (Higher example style)
   ============================================================ */
.worked {
  background: var(--surface-2);
  border: 1px solid var(--border-accent);
  border-left: 5px solid var(--accent);
  border-radius: 12px;
  padding: 0.85rem 1rem;
  margin: 0.8rem 0;
}
.worked p { margin: 0.3rem 0; }
table.rule-table { width: 100%; border-collapse: collapse; margin: 0.8rem 0; }
table.rule-table th, table.rule-table td {
  border: 1px solid var(--border-soft);
  padding: 0.55rem 0.65rem;
  text-align: left;
  vertical-align: top;
}
table.rule-table th { background: var(--surface-2); font-weight: 900; color: var(--text); }

/* ============================================================
   V–I GRAPHS
   ============================================================ */
.vi-graphs { display: grid; gap: 1rem; grid-template-columns: 1fr; }
@media (min-width: 560px) { .vi-graphs { grid-template-columns: 1fr 1fr; } }
.vi-card { text-align: center; }
.vi-svg { width: 100%; max-width: 220px; height: auto; color: var(--text); }
.vi-card p { margin: 0.3rem 0 0; font-size: 0.9rem; }

/* ============================================================
   REVEAL ANSWER (Higher chevron style)
   ============================================================ */
details.reveal {
  border: 1px solid var(--border-accent);
  border-radius: 10px;
  background: var(--card);
  margin: 0.5rem 0;
  overflow: hidden;
}
details.reveal > summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  min-height: 44px;
  padding: 0.6rem 0.8rem;
  font-weight: 900;
  color: var(--text);
  background: var(--surface-2);
}
details.reveal > summary::-webkit-details-marker { display: none; }
details.reveal > summary::after {
  content: "▾";
  margin-left: auto;
  font-weight: 900;
  opacity: .8;
  transition: transform .18s ease;
}
details.reveal[open] > summary::after { transform: rotate(180deg); }
.reveal-body { padding: 0.65rem 0.8rem; color: var(--muted); font-weight: 800; line-height: 1.55; }

/* ============================================================
   QUIZ (Higher .opt style)
   ============================================================ */
.quiz-q { margin: 1.1rem 0; }
.quiz-q > p { margin: 0 0 0.5rem; font-weight: 900; color: var(--text); }
.quiz-opts { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.quiz-opt {
  padding: 0.6rem 0.85rem;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  background: var(--card);
  color: var(--text);
  cursor: pointer;
  font-family: var(--font-stack);
  font-size: 1rem;
  font-weight: 800;
  min-height: 44px;
  transition: border-color 0.15s ease, transform 0.12s ease;
}
.quiz-opt:hover:not(:disabled) { border-color: var(--border-strong); transform: translateY(-1px); }
.quiz-opt:disabled { cursor: default; }
.quiz-opt.correct { border-color: var(--good); background: rgba(21,128,61,0.14); color: var(--text); }
.quiz-opt.wrong   { border-color: var(--warm); background: rgba(194,65,12,0.12); color: var(--text); }
.quiz-fb { margin-top: 0.5rem; font-weight: 900; min-height: 1.2em; }
.quiz-score { font-weight: 900; margin-top: 0.8rem; color: var(--text); }

/* ============================================================
   GREEN / AMBER / RED SELF-CHECK (Higher .rag style)
   ============================================================ */
.gar-level { margin-top: 0.8rem; }
.gar-level h3 { margin: 0.7rem 0 0.2rem; font-weight: 900; color: var(--text); }
.gar-row {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  justify-content: space-between;
  flex-wrap: wrap;
  padding: 0.55rem 0.1rem;
  border-bottom: 1px solid var(--border-soft);
}
.gar-crit { flex: 1; min-width: 60%; font-weight: 800; color: var(--text); }
.gar-btns { display: inline-flex; gap: 0.35rem; }
.gar-btn {
  min-width: 44px; min-height: 44px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  font-weight: 900;
  cursor: pointer;
  font-family: var(--font-stack);
}
.gar-btn.g.on { background: #1a9e57; color: #fff; border-color: transparent; }
.gar-btn.a.on { background: #b45309; color: #fff; border-color: transparent; }
.gar-btn.r.on { background: #c0392b; color: #fff; border-color: transparent; }
.gar-btn.on { outline: 2px solid var(--text); outline-offset: 2px; }
.gar-reset {
  margin-top: 0.8rem;
  min-height: 44px;
  background: var(--card);
  border: 1px solid var(--border-accent);
  border-radius: 10px;
  padding: 0.5rem 0.95rem;
  color: var(--text);
  font-family: var(--font-stack);
  font-weight: 900;
  cursor: pointer;
}
.gar-reset:hover { border-color: var(--border-strong); }

/* ============================================================
   VIDEO GRID
   ============================================================ */
.video-grid { padding: 1rem 1.1rem 1.2rem; display: grid; gap: 1rem; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 700px) { .video-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.video-group-title { grid-column: 1 / -1; margin: 0.4rem 0 -0.2rem; font-weight: 900; color: var(--accent-2); }
.video-card { background: var(--surface-2); border-radius: 12px; border: 1px solid var(--border-accent); padding: 0.75rem; }
.video-title { font-weight: 900; margin: 0 0 0.5rem; font-size: 0.95rem; }
.video-embed { position: relative; width: 100%; padding-top: 56.25%; border-radius: 0.7rem; overflow: hidden; }
.video-embed iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }

/* ============================================================
   BUTTONS & LINKS (Higher .btn style)
   ============================================================ */
.download-btn, .ai-tutor-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  min-height: 48px;
  padding: 0.6rem 1.1rem;
  background: var(--card);
  border: 1px solid var(--border-accent);
  border-radius: 12px;
  font-weight: 900;
  color: var(--text);
  text-decoration: none;
  box-shadow: var(--shadow-soft);
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
}
.download-btn:hover, .download-btn:focus-visible,
.ai-tutor-btn:hover, .ai-tutor-btn:focus-visible {
  transform: translateY(-1px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-hover);
}

.tools-link {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.1rem 1.3rem;
  background: var(--surface-2);
  border: 1px solid var(--border-accent);
  border-radius: 14px;
  color: var(--text);
  text-decoration: none;
  box-shadow: var(--shadow-soft);
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
}
.tools-link:hover, .tools-link:focus-visible {
  transform: translateY(-2px);
  border-color: var(--border-strong);
  box-shadow: var(--shadow-hover);
}
.tools-link .tl-icon { font-size: 2rem; }
.tools-link .tl-title { font-weight: 900; font-size: 1.1rem; color: var(--accent-2); }
.tools-link .tl-sub { font-size: 0.9rem; color: var(--muted); font-weight: 700; }

/* primary action buttons → teal gradient pill (mirrors Higher .btn.primary) */
.vir-btn {
  margin-left: 0.5rem;
  margin-top: 0.4rem;
  min-height: 44px;
  padding: 0.55rem 1rem;
  border-radius: 10px;
  border: 1px solid transparent;
  background: linear-gradient(135deg, var(--cta-1), var(--cta-2));
  color: #fff;
  font-weight: 900;
  cursor: pointer;
  font-family: var(--font-stack);
  font-size: 1rem;
  transition: filter 0.15s ease, transform 0.15s ease;
}
.vir-btn:hover { filter: brightness(1.06); transform: translateY(-1px); }

.summary-grid-item {
  padding: 0.6rem;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  background: var(--surface-2);
  color: var(--text);
}

/* ============================================================
   FORM INPUTS / SELECTS
   ============================================================ */
input, select {
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.5rem;
  font-family: var(--font-stack);
  font-size: 1rem;
}

/* JS feedback colours */
.fb-correct { color: var(--good); font-weight: 900; }
.fb-incorrect { color: var(--warm); font-weight: 900; }
.fb-warning { color: #92400e; font-weight: 900; }
@media (prefers-color-scheme: dark) { .fb-warning { color: #ffca6f; } }

/* ============================================================
   TILES (hub roadmap) — Higher card feel
   ============================================================ */
.tile-grid {
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(auto-fit, minmax(min(260px, 100%), 1fr));
  margin-top: 0.8rem;
  align-items: stretch;
}
.tile {
  display: block;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background:
    radial-gradient(420px 180px at 20% 0%, var(--glow-1), transparent 70%),
    var(--card);
  box-shadow: var(--shadow-soft);
  text-decoration: none;
  color: var(--text);
  overflow: hidden;
  min-height: 144px;
  position: relative;
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}
.tile:hover, .tile:focus-visible {
  transform: translateY(-2px);
  box-shadow: var(--shadow-hover);
  border-color: var(--border-strong);
}
.tile:active { transform: translateY(1px); }
.tile.wip { border-style: dashed; opacity: 0.9; }
.tile-inner {
  padding: 15px 14px 13px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  height: 100%;
  justify-content: space-between;
}
.tile-title {
  margin: 0;
  font-size: 1.02rem;
  font-weight: 900;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  line-height: 1.3;
  color: var(--text);
}
.tile-desc { margin: 0; color: var(--muted); font-weight: 800; line-height: 1.45; }

/* badges / tags (hub) */
.badge {
  display: inline-block;
  padding: 0.16rem 0.6rem;
  border-radius: 999px;
  border: 1px solid var(--border-soft);
  background: var(--surface-2);
  font-size: 0.82rem;
  font-weight: 900;
  color: var(--text);
  white-space: nowrap;
}
.badge.practical { border: 1.5px solid rgba(255,176,32,0.45); background: rgba(255,176,32,0.14); }
.badge.soon { border: 1px dashed var(--border); background: var(--surface-2); color: var(--muted); }

/* extra-links accordion (hub) */
details.block {
  border-radius: 16px;
  border: 1px solid var(--border-accent);
  background: var(--surface-2);
  overflow: hidden;
  box-shadow: var(--shadow-soft);
  margin-top: 0.8rem;
}
details.block > summary {
  cursor: pointer;
  padding: 0.95rem 1rem;
  font-weight: 900;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  background: var(--summary-bg);
  border-bottom: 1px solid var(--border-soft);
}
details.block > summary::-webkit-details-marker { display: none; }
.details-inner { padding: 12px 12px 14px; }
.tag {
  display: inline-block;
  font-size: 0.85rem;
  padding: 4px 10px;
  border-radius: 999px;
  border: 1px solid var(--border-soft);
  background: var(--surface-2);
  color: var(--text);
  white-space: nowrap;
  font-weight: 900;
}

/* ============================================================
   FOOTER
   ============================================================ */
footer {
  text-align: center;
  padding: 1rem;
  background: var(--footer-bg);
  border-top: 1px solid var(--border-soft);
  font-size: 0.92rem;
  color: var(--muted);
  margin-top: auto;
  font-weight: 800;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 700px) {
  .page-wrap { padding: 0 10px 4rem; }
  .panel, .topic-box { padding: 1rem; }
  .tile { min-height: 140px; }
  .tile-grid { gap: 10px; }
}