/* PlaitoMaths design tokens — tablet-first, calm academic palette.
   Shared across all pages. */
:root {
  /* palette */
  --bg:        #f4f6fb;
  --bg-grad:   linear-gradient(180deg, #f7f9fd 0%, #eef1f8 100%);
  --surface:   #ffffff;
  --surface-2: #f8fafc;
  --border:    #e3e8f0;
  --border-2:  #d6deea;

  --ink:       #1c2433;   /* primary text */
  --ink-2:     #55617a;   /* secondary text */
  --ink-3:     #8a95ab;   /* muted */

  --brand:     #4f46e5;   /* indigo */
  --brand-700: #4338ca;
  --brand-50:  #eef0fe;
  --teal:      #0e9488;
  --amber:     #d97706;

  --ok:        #16a34a;
  --ok-bg:     #ecfdf3;
  --bad:       #dc2626;
  --bad-bg:    #fef2f2;

  /* maths / thinking / reading accents */
  --c-maths:    #4f46e5;
  --c-thinking: #0e9488;
  --c-reading:  #d97706;

  /* type */
  --font: "Segoe UI", system-ui, -apple-system, Roboto, "Helvetica Neue", sans-serif;
  --fs-sm: 0.85rem;
  --fs-md: 1rem;
  --fs-lg: 1.2rem;
  --fs-xl: 1.55rem;

  /* spacing / shape */
  --sp-1: 4px; --sp-2: 8px; --sp-3: 12px; --sp-4: 16px;
  --sp-5: 20px; --sp-6: 24px; --sp-7: 32px; --sp-8: 44px;
  --r-sm: 8px; --r-md: 12px; --r-lg: 18px; --r-pill: 999px;

  --shadow-sm: 0 1px 2px rgba(20,30,55,.06), 0 1px 3px rgba(20,30,55,.05);
  --shadow-md: 0 4px 14px rgba(20,30,55,.08), 0 2px 6px rgba(20,30,55,.05);
  --shadow-lg: 0 14px 40px rgba(20,30,55,.12), 0 4px 14px rgba(20,30,55,.06);
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }   /* keep the hidden attr authoritative over display rules */
html { font-size: 17px; }
body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg-grad);
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}
h1, h2, h3 { line-height: 1.2; margin: 0 0 var(--sp-3); }
a { color: var(--brand); }

/* buttons */
.btn {
  appearance: none; border: 0; cursor: pointer;
  font: inherit; font-weight: 700;
  padding: 13px 26px; border-radius: var(--r-md);
  background: linear-gradient(135deg, var(--brand-700), var(--brand));
  color: #fff; box-shadow: 0 4px 12px rgba(79,70,229,.28);
  transition: filter .12s, transform .08s, box-shadow .12s;
}
.btn:hover { filter: brightness(1.07); }
.btn:active { transform: scale(.98); }
.btn[disabled] { opacity: .45; cursor: not-allowed; filter: none; box-shadow: none; }
.btn.ghost {
  background: var(--surface); color: var(--ink);
  border: 1.5px solid var(--border-2); box-shadow: var(--shadow-sm);
}
.btn.ghost:hover { background: var(--surface-2); filter: none; }

.tag {
  display: inline-block; font-size: var(--fs-sm); font-weight: 700;
  padding: 4px 12px; border-radius: var(--r-pill);
  background: var(--brand-50); color: var(--brand-700);
}

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