/* =========================================================================
   Magic & Math with Cards — shared stylesheet
   Visual world: warm paper page for reading; a deep-ink "stage" (the card
   table) for every interactive. Cards are always paper. Colour has stable
   meaning (see DESIGN.md): active = teal, invariant = gold, counterexample =
   coral. Suit ink red/black is a literal card property, never right/wrong.
   ========================================================================= */

/* Suit symbols (and ⊕) from a tiny DejaVu Sans subset, so ♣♦♥♠ never fall back to emoji or a mismatched system face */
@font-face { font-family: "MMC Symbols"; src: url("../fonts/mmc-symbols.woff2") format("woff2"); unicode-range: U+2660-2667, U+2295; font-display: block; }
@font-face { font-family: "Fraunces"; src: url("../fonts/fraunces-latin-full-normal.woff2") format("woff2"); font-weight: 100 900; font-style: normal; font-display: swap; }
@font-face { font-family: "Fraunces"; src: url("../fonts/fraunces-latin-full-italic.woff2") format("woff2"); font-weight: 100 900; font-style: italic; font-display: swap; }
@font-face { font-family: "Source Sans 3"; src: url("../fonts/source-sans-3-latin-wght-normal.woff2") format("woff2"); font-weight: 200 900; font-style: normal; font-display: swap; }
@font-face { font-family: "Source Sans 3"; src: url("../fonts/source-sans-3-latin-wght-italic.woff2") format("woff2"); font-weight: 200 900; font-style: italic; font-display: swap; }
@font-face { font-family: "STIX Two Text"; src: url("../fonts/stix-two-text-latin-400-normal.woff2") format("woff2"); font-weight: 400; font-style: normal; font-display: swap; }
@font-face { font-family: "STIX Two Text"; src: url("../fonts/stix-two-text-latin-400-italic.woff2") format("woff2"); font-weight: 400; font-style: italic; font-display: swap; }

:root {
  /* Course tokens (production/design-tokens.json) */
  --stage: #101820;
  --stage-raised: #17222C;
  --paper: #F4EFE4;
  --paper-shade: #E9E2D3;
  --secondary-on-stage: #A9B7C3;
  --structure: #566875;
  --active: #68D8C1;
  --invariant: #F2C66D;
  --counter: #F1847D;
  --red-ink: #B6263D;
  --black-ink: #17212B;
  --card-back: #23415A;
  --card-back-line: #33597A;

  /* Page (reading surface) */
  --page: #F7F3EA;
  --page-raised: #FFFDF8;
  --text: #17212B;
  --text-2: #4B5A66;
  --text-3: #6E7C87;
  --rule: rgba(23, 33, 43, 0.12);
  --rule-strong: rgba(23, 33, 43, 0.22);
  /* Semantic accents tuned for reading on paper */
  --active-on-page: #1C7A68;
  --invariant-on-page: #8A5F06;
  --counter-on-page: #B0413A;
  --focus: #1C7A68;

  /* Type */
  --font-display: "MMC Symbols", "Fraunces", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --font-ui: "MMC Symbols", "Source Sans 3", "Source Sans Pro", -apple-system, "Segoe UI", "Segoe UI Symbol", "Apple Symbols", "Noto Sans Symbols 2", "DejaVu Sans", system-ui, sans-serif;
  --font-math: "MMC Symbols", "STIX Two Text", "Cambria Math", "Times New Roman", serif;

  /* Spacing scale: 8 16 24 40 64 96 */
  --s1: 8px; --s2: 16px; --s3: 24px; --s4: 40px; --s5: 64px; --s6: 96px;

  /* Motion */
  --ease-out: cubic-bezier(0.19, 1, 0.22, 1);
  --ease-in-out: cubic-bezier(0.645, 0.045, 0.355, 1);
  --ease-press: cubic-bezier(0.25, 0.46, 0.45, 0.94);

  /* Card geometry: override --card-w on any container */
  --card-w: clamp(46px, 8.4vw, 84px);
  --card-ratio: 1.4;

  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --page: #0C1217;
    --page-raised: #121A21;
    --text: #EDE7DA;
    --text-2: #AEB9C2;
    --text-3: #85929C;
    --rule: rgba(237, 231, 218, 0.10);
    --rule-strong: rgba(237, 231, 218, 0.20);
    --active-on-page: #68D8C1;
    --invariant-on-page: #F2C66D;
    --counter-on-page: #F1847D;
    --focus: #68D8C1;
    --stage: #101820;
    --stage-raised: #18232D;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --page: #0C1217;
  --page-raised: #121A21;
  --text: #EDE7DA;
  --text-2: #AEB9C2;
  --text-3: #85929C;
  --rule: rgba(237, 231, 218, 0.10);
  --rule-strong: rgba(237, 231, 218, 0.20);
  --active-on-page: #68D8C1;
  --invariant-on-page: #F2C66D;
  --counter-on-page: #F1847D;
  --focus: #68D8C1;
  --stage-raised: #18232D;
  color-scheme: dark;
}

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--page);
  color: var(--text);
  font-family: var(--font-ui);
  font-size: 1.125rem;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  font-variant-emoji: text; /* suit symbols ♥♦ as text, never as emoji */
}
img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration-thickness: 1px; text-underline-offset: 3px; text-decoration-color: var(--rule-strong); }
a:hover { text-decoration-color: currentColor; }
:focus-visible { outline: 2px solid var(--focus); outline-offset: 3px; border-radius: 4px; }
::selection { background: color-mix(in oklch, var(--invariant) 45%, transparent); }

h1, h2, h3 { font-family: var(--font-display); font-weight: 500; line-height: 1.12; margin: 0; font-optical-sizing: auto; text-wrap: balance; }
h1 { font-size: clamp(2.3rem, 5.6vw, 4rem); letter-spacing: -0.015em; font-variation-settings: "SOFT" 50, "WONK" 0; }
h2 { font-size: clamp(1.6rem, 3.4vw, 2.25rem); letter-spacing: -0.01em; }
h3 { font-size: 1.3rem; font-family: var(--font-ui); font-weight: 650; letter-spacing: 0; }
p { margin: 0; text-wrap: pretty; }
.math, var { font-family: var(--font-math); font-style: italic; font-size: 1.08em; }
.math-up { font-family: var(--font-math); font-style: normal; }
.num { font-variant-numeric: tabular-nums; }
kbd { font-family: var(--font-ui); font-size: 0.85em; border: 1px solid var(--rule-strong); border-bottom-width: 2px; border-radius: 4px; padding: 0 5px; }

[hidden] { display: none !important; }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.skip-link { position: absolute; left: 16px; top: -48px; background: var(--text); color: var(--page); padding: 8px 12px; border-radius: 6px; z-index: 100; }
.skip-link:focus { top: 12px; }

/* ---------- Site chrome ---------- */
.site-header {
  display: flex; align-items: center; justify-content: space-between; gap: var(--s2);
  max-width: 1180px; margin: 0 auto; padding: var(--s2) var(--s2);
  font-size: 0.95rem;
}
.wordmark { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; font-family: var(--font-display); font-size: 1.15rem; font-weight: 500; }
.wordmark-pip { width: 18px; height: 25px; border-radius: 3px; background: var(--paper); border: 1px solid var(--rule-strong); position: relative; flex: none; }
.wordmark-pip::after { content: "♠"; position: absolute; inset: 0; display: grid; place-items: center; font-size: 13px; color: var(--black-ink); }
.site-nav { display: flex; gap: var(--s3); }
.site-nav a { text-decoration: none; color: var(--text-2); padding: 10px 0; }
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--text); }

.site-footer { border-top: 1px solid var(--rule); margin-top: var(--s6); }
.site-footer-inner { max-width: 1180px; margin: 0 auto; padding: var(--s4) var(--s2) var(--s5); display: flex; flex-wrap: wrap; gap: var(--s2) var(--s4); justify-content: space-between; color: var(--text-2); font-size: 0.95rem; }

/* ---------- Layout ---------- */
.wrap { max-width: 1180px; margin: 0 auto; padding: 0 var(--s2); }
.prose { max-width: 66ch; }
.prose > * + * { margin-top: 1em; }
.prose h2 + *, .prose h3 + * { margin-top: 0.6em; }
.prose ul, .prose ol { padding-left: 1.3em; }
.prose li + li { margin-top: 0.4em; }
.lede { font-size: clamp(1.2rem, 2.2vw, 1.4rem); color: var(--text-2); line-height: 1.5; max-width: 52ch; }
.eyebrow { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.12em; color: var(--text-3); font-weight: 600; }

/* ---------- Trick page ---------- */
.trick-hero { padding: var(--s5) 0 var(--s4); display: grid; gap: var(--s3); }
.trick-hero .lede { margin-top: var(--s1); }
.trick-meta { display: flex; flex-wrap: wrap; gap: var(--s1) var(--s4); color: var(--text-2); font-size: 0.98rem; margin-top: var(--s1); }
.trick-meta dt { font-size: 0.75rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--text-3); font-weight: 600; }
.trick-meta dd { margin: 0; }

.trick-section { padding: var(--s5) 0 0; }
.trick-section > .section-head { display: grid; gap: var(--s1); margin-bottom: var(--s3); max-width: 66ch; }
.section-head .step-no { font-family: var(--font-display); font-style: italic; color: var(--text-3); font-size: 1.05rem; }

/* The decisive sentence: one per explanation */
.key-idea {
  border-left: 3px solid var(--invariant-on-page);
  padding: 4px 0 4px var(--s2);
  font-family: var(--font-display); font-size: clamp(1.25rem, 2.4vw, 1.55rem); line-height: 1.35;
  max-width: 44ch;
}
.note { color: var(--text-2); font-size: 0.98rem; }
.label-active { color: var(--active-on-page); font-weight: 600; }
.label-invariant { color: var(--invariant-on-page); font-weight: 600; }
.label-counter { color: var(--counter-on-page); font-weight: 600; }

/* ---------- The curtain (secret gate) ---------- */
.curtain { margin: var(--s5) 0 0; display: grid; justify-items: center; gap: var(--s2); text-align: center; position: relative; }
.curtain::before { content: ""; position: absolute; left: 0; right: 0; top: 50%; border-top: 1px dashed var(--rule-strong); z-index: 0; }
.curtain > * { position: relative; z-index: 1; }
.curtain .btn:not(.btn-primary) { background: var(--page); }
.curtain-note { color: var(--text-3); font-size: 0.92rem; background: var(--page); padding: 0 var(--s1); }
.secret[hidden] { display: none; }
.secret.is-revealing { animation: curtain-rise 700ms var(--ease-out) both; }
@keyframes curtain-rise { from { opacity: 0; transform: translateY(12px); clip-path: inset(0 0 100% 0); } to { opacity: 1; transform: none; clip-path: inset(0 0 0 0); } }

/* ---------- Buttons & controls ---------- */
.btn {
  --btn-bg: transparent; --btn-fg: var(--text); --btn-border: var(--rule-strong);
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  min-height: 44px; padding: 0 18px; border-radius: 8px;
  border: 1px solid var(--btn-border); background: var(--btn-bg); color: var(--btn-fg);
  font: 600 1rem/1 var(--font-ui); cursor: pointer; text-decoration: none; white-space: nowrap;
  transition: transform 150ms var(--ease-press), background-color 150ms ease, border-color 150ms ease, color 150ms ease, opacity 150ms ease;
  -webkit-tap-highlight-color: transparent; user-select: none;
}
.btn:active:not(:disabled) { transform: scale(0.97); }
.btn:disabled, .btn[aria-disabled="true"] { cursor: not-allowed; opacity: 0.45; }
.btn-primary { --btn-bg: var(--text); --btn-fg: var(--page); --btn-border: var(--text); }
.btn-primary:hover:not(:disabled) { --btn-bg: color-mix(in oklch, var(--text) 86%, var(--page)); }
@media (hover: hover) and (pointer: fine) { .btn-ghost:hover:not(:disabled) { --btn-border: var(--text-2); } }
.btn-sm { min-height: 36px; padding: 0 12px; font-size: 0.92rem; }
@media (pointer: coarse), (max-width: 720px) { .btn-sm { min-height: 44px; } }
.btn-link { border: 0; padding: 0 4px; min-height: 44px; text-decoration: underline; text-underline-offset: 3px; text-decoration-color: var(--rule-strong); background: none; }

.controls { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.field { display: inline-flex; flex-direction: column; gap: 4px; font-size: 0.85rem; color: var(--text-2); }
.field input, .field select {
  min-height: 44px; border-radius: 8px; border: 1px solid var(--rule-strong); background: var(--page-raised); color: var(--text);
  font: 500 1rem var(--font-ui); padding: 0 12px;
}
.field input[type="number"] { width: 6.5em; font-variant-numeric: tabular-nums; }
.segmented { display: inline-flex; border: 1px solid var(--rule-strong); border-radius: 8px; padding: 3px; gap: 3px; }
.segmented button { min-height: 44px; min-width: 44px; padding: 0 12px; border: 0; border-radius: 6px; background: none; color: var(--text-2); font: 600 0.95rem var(--font-ui); cursor: pointer; }
.segmented button[aria-pressed="true"] { background: var(--text); color: var(--page); }

/* ---------- The stage (card table) ---------- */
.stage {
  --btn-fg: var(--paper);
  background: var(--stage);
  color: var(--paper);
  border-radius: 14px;
  padding: var(--s3) var(--s2);
  position: relative;
  box-shadow: 0 1px 0 rgba(255,255,255,0.04) inset;
}
@media (min-width: 720px) { .stage { padding: var(--s4) var(--s4); } }
.stage + .stage, .stage + .controls, .controls + .stage { margin-top: var(--s2); }
.stage .btn { --btn-fg: var(--paper); --btn-border: rgba(244, 239, 228, 0.28); }
.stage .btn-primary { --btn-bg: var(--paper); --btn-fg: var(--stage); --btn-border: var(--paper); }
.stage .btn-primary:hover:not(:disabled) { --btn-bg: #FFFFFF; }
@media (hover: hover) and (pointer: fine) { .stage .btn-ghost:hover:not(:disabled) { --btn-border: rgba(244, 239, 228, 0.6); } }
.stage .segmented { border-color: rgba(244,239,228,0.25); }
.stage .segmented button { color: var(--secondary-on-stage); }
.stage .segmented button[aria-pressed="true"] { background: var(--paper); color: var(--stage); }
.stage .field { color: var(--secondary-on-stage); }
.stage .field input, .stage .field select { background: var(--stage-raised); color: var(--paper); border-color: rgba(244,239,228,0.25); }
.stage :focus-visible { outline-color: var(--active); }
.stage-caption { color: var(--secondary-on-stage); font-size: 1rem; line-height: 1.5; max-width: 62ch; }
.stage-title { font-family: var(--font-display); font-size: clamp(1.25rem, 2.4vw, 1.6rem); line-height: 1.25; color: var(--paper); }
.stage-instruction { font-size: 1.15rem; line-height: 1.45; color: var(--paper); max-width: 56ch; min-height: 3em; }
.stage-instruction strong { color: var(--active); font-weight: 600; }
.stage-row { display: flex; flex-wrap: wrap; gap: var(--s2); align-items: center; }
.stage-stack > * + * { margin-top: var(--s3); }
.stage hr { border: 0; border-top: 1px solid rgba(244,239,228,0.12); margin: var(--s3) 0; }

/* Readouts & ledgers on stage */
.readout { display: inline-flex; flex-direction: column; gap: 2px; min-width: 6ch; }
.readout-label { font-size: 0.75rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--secondary-on-stage); font-weight: 600; }
.readout-value { font-family: var(--font-math); font-size: 1.7rem; line-height: 1.1; font-variant-numeric: tabular-nums; }
.readout-value.is-invariant { color: var(--invariant); }
.readout-value.is-active { color: var(--active); }
.ledger { list-style: none; margin: 0; padding: 0; font-size: 0.95rem; color: var(--secondary-on-stage); display: grid; gap: 4px; max-height: 14em; overflow: auto; font-variant-numeric: tabular-nums; }
.ledger li { display: flex; gap: 10px; }
.ledger li::before { content: counter(ledger) "."; counter-increment: ledger; color: var(--structure); min-width: 2ch; text-align: right; }
.ledger { counter-reset: ledger; }
.ledger li:last-child { color: var(--paper); }
.chip { display: inline-flex; align-items: center; gap: 6px; padding: 2px 10px; border-radius: 999px; font-size: 0.85rem; font-weight: 600; border: 1px solid rgba(244,239,228,0.25); color: var(--secondary-on-stage); }
.chip.is-active { border-color: var(--active); color: var(--active); }
.chip.is-invariant { border-color: var(--invariant); color: var(--invariant); }
.chip.is-counter { border-color: var(--counter); color: var(--counter); }
.verdict { border-left: 3px solid var(--structure); padding: 6px 0 6px 14px; font-size: 1.05rem; line-height: 1.45; max-width: 60ch; }
.verdict.is-invariant { border-color: var(--invariant); }
.verdict.is-active { border-color: var(--active); }
.verdict.is-counter { border-color: var(--counter); }
.verdict .verdict-title { display: block; font-weight: 650; color: var(--paper); }
.legend { display: flex; flex-wrap: wrap; gap: 6px 18px; font-size: 0.88rem; color: var(--secondary-on-stage); }
.legend .swatch { display: inline-block; width: 12px; height: 12px; border-radius: 3px; margin-right: 6px; vertical-align: -1px; }

/* Piles, rows and slots for cards */
.pile-row { display: flex; flex-wrap: wrap; gap: var(--s2) var(--s3); align-items: flex-start; }
.pile { display: grid; justify-items: start; gap: 8px; }
.pile-label { font-size: 0.8rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--secondary-on-stage); font-weight: 600; text-align: center; }
.card-row { display: flex; flex-wrap: wrap; gap: 8px; align-items: flex-end; min-height: calc(var(--card-w) * var(--card-ratio)); }
.card-row.tight { gap: 4px; }
.card-row.overlap { flex-wrap: nowrap; gap: 0; }
.card-row.overlap > .card + .card { margin-left: calc(var(--card-w) * -0.62); }
.card-stack { position: relative; width: var(--card-w); height: calc(var(--card-w) * var(--card-ratio)); }
.card-stack > .card { position: absolute; left: 0; top: 0; }
.slot { width: var(--card-w); height: calc(var(--card-w) * var(--card-ratio)); border-radius: calc(var(--card-w) * 0.09); border: 1.5px dashed rgba(244,239,228,0.22); display: grid; place-items: center; color: var(--structure); font-size: 0.8rem; }
.slot.is-target { border-color: var(--active); border-style: solid; background: color-mix(in oklch, var(--active) 10%, transparent); }
.top-marker { font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--secondary-on-stage); font-weight: 700; display: inline-flex; align-items: center; gap: 4px; }
.top-marker::before { content: "▲"; font-size: 0.6rem; }

/* ---------- Playing cards ---------- */
.card {
  --w: var(--card-w);
  width: var(--w); height: calc(var(--w) * var(--card-ratio));
  position: relative; flex: none;
  perspective: calc(var(--w) * 12);
  border-radius: calc(var(--w) * 0.09);
  -webkit-tap-highlight-color: transparent;
}
.card-tilt { position: absolute; inset: 0; transition: transform 220ms var(--ease-out); border-radius: inherit; }
.card-inner { position: absolute; inset: 0; transform-style: preserve-3d; transition: transform 460ms var(--ease-in-out); border-radius: inherit; }
.card[data-face="down"] .card-inner { transform: rotateY(180deg); }
.face {
  position: absolute; inset: 0; border-radius: inherit; backface-visibility: hidden; -webkit-backface-visibility: hidden; overflow: hidden;
  box-shadow: 0 1px 1px rgba(0,0,0,0.25), 0 3px 8px rgba(0,0,0,0.18);
}
.face.front { background: var(--paper); color: var(--black-ink); }
.card[data-color="red"] .face.front { color: var(--red-ink); }
.face.back {
  transform: rotateY(180deg);
  background: var(--paper);
  padding: calc(var(--w) * 0.06);
}
.face.back::before {
  content: ""; position: absolute; inset: calc(var(--w) * 0.06); border-radius: calc(var(--w) * 0.05);
  background-color: var(--card-back);
  background-image:
    repeating-linear-gradient(45deg, transparent 0 calc(var(--w) * 0.07), var(--card-back-line) calc(var(--w) * 0.07) calc(var(--w) * 0.085)),
    repeating-linear-gradient(-45deg, transparent 0 calc(var(--w) * 0.07), var(--card-back-line) calc(var(--w) * 0.07) calc(var(--w) * 0.085));
}
.face.back::after {
  content: ""; position: absolute; left: 50%; top: 50%; width: calc(var(--w) * 0.26); height: calc(var(--w) * 0.26);
  transform: translate(-50%, -50%) rotate(45deg); border: 1.5px solid var(--invariant); background: var(--card-back); opacity: 0.9;
}
.corner { position: absolute; display: grid; justify-items: center; line-height: 0.92; font-weight: 700; font-family: var(--font-ui); }
.corner .r { font-size: calc(var(--w) * 0.24); letter-spacing: -0.04em; }
.corner .s { font-size: calc(var(--w) * 0.2); }
.corner.tl { left: calc(var(--w) * 0.07); top: calc(var(--w) * 0.07); }
.corner.br { right: calc(var(--w) * 0.07); bottom: calc(var(--w) * 0.07); transform: rotate(180deg); }
.pip { position: absolute; inset: 0; display: grid; place-items: center; font-size: calc(var(--w) * 0.5); line-height: 1; }
.pip.court { font-family: var(--font-display); font-size: calc(var(--w) * 0.52); font-weight: 500; font-style: italic; }
.pip.court::after { content: ""; position: absolute; inset: calc(var(--w) * 0.3) calc(var(--w) * 0.29); border: 1px solid currentColor; border-radius: calc(var(--w) * 0.04); opacity: 0.25; }
/* Colour-only card (no rank/suit) */
.card[data-kind="color"] .face.front { background: var(--paper); }
.card[data-kind="color"] .pip { font-size: calc(var(--w) * 0.36); font-family: var(--font-ui); font-weight: 700; }
.card[data-kind="color"][data-color="red"] .face.front { box-shadow: inset 0 0 0 calc(var(--w) * 0.06) var(--paper), inset 0 0 0 calc(var(--w) * 0.5) color-mix(in oklch, var(--red-ink) 14%, var(--paper)), 0 1px 1px rgba(0,0,0,0.25), 0 3px 8px rgba(0,0,0,0.18); }
.card[data-kind="color"][data-color="black"] .face.front { box-shadow: inset 0 0 0 calc(var(--w) * 0.06) var(--paper), inset 0 0 0 calc(var(--w) * 0.5) color-mix(in oklch, var(--black-ink) 10%, var(--paper)), 0 1px 1px rgba(0,0,0,0.25), 0 3px 8px rgba(0,0,0,0.18); }
/* Label card (numbers, letters, words — e.g. the 124-card labels) */
.card[data-kind="label"] .pip { font-family: var(--font-math); font-size: calc(var(--w) * 0.42); font-variant-numeric: tabular-nums; }

/* Rings (semantic highlight) — never recolour the card itself */
.card[data-ring]::after { content: ""; position: absolute; inset: -4px; border-radius: calc(var(--w) * 0.09 + 4px); border: 2.5px solid transparent; pointer-events: none; transition: border-color 160ms ease; }
.card[data-ring="active"]::after { border-color: var(--active); }
.card[data-ring="invariant"]::after { border-color: var(--invariant); }
.card[data-ring="counter"]::after { border-color: var(--counter); }
.card[data-ring="structure"]::after { border-color: var(--structure); border-style: dashed; }
/* Tags (A/B source, position numbers) sit above the card */
.card-tag { position: absolute; left: 50%; bottom: calc(100% + 4px); transform: translateX(-50%); font-size: 0.72rem; font-weight: 700; letter-spacing: 0.04em; color: var(--secondary-on-stage); white-space: nowrap; pointer-events: none; }
.card-tag[data-kind="active"] { color: var(--active); }
.card-tag[data-kind="invariant"] { color: var(--invariant); }
.card-tag[data-kind="counter"] { color: var(--counter); }
.card-tag.below { bottom: auto; top: calc(100% + 4px); }

/* Interactive cards */
button.card { padding: 0; border: 0; background: none; cursor: pointer; color: inherit; font: inherit; }
button.card:disabled { cursor: default; }
@media (hover: hover) and (pointer: fine) {
  button.card:not(:disabled):hover .card-tilt { transform: translateY(-6px); }
}
button.card:active:not(:disabled) .card-tilt { transform: translateY(-2px) scale(0.98); }
.card.is-selected .card-tilt { transform: translateY(calc(var(--w) * -0.14)) rotate(-3deg); }
.card.is-lean .card-tilt { transform: rotate(-3deg); }
.card.is-dim { opacity: 0.38; }
.card.is-ghost { opacity: 0.0; }

/* On paper pages (outside stage), cards need a little more edge */
.card .face.front { box-shadow: 0 0 0 1px rgba(23,33,43,0.10), 0 1px 1px rgba(0,0,0,0.18), 0 3px 8px rgba(0,0,0,0.12); }
.stage .card .face.front { box-shadow: 0 1px 1px rgba(0,0,0,0.3), 0 4px 10px rgba(0,0,0,0.28); }

/* ---------- Tables ---------- */
.table-wrap { overflow-x: auto; }
table.data { border-collapse: collapse; font-variant-numeric: tabular-nums; font-size: 0.98rem; }
table.data th, table.data td { padding: 6px 12px; border-bottom: 1px solid var(--rule); text-align: left; }
table.data th { font-weight: 650; color: var(--text-2); font-size: 0.85rem; letter-spacing: 0.04em; }
.stage table.data th, .stage table.data td { border-color: rgba(244,239,228,0.12); }
.stage table.data th { color: var(--secondary-on-stage); }

/* ---------- Disclosure ---------- */
details.more { border-top: 1px solid var(--rule); padding: var(--s2) 0; max-width: 66ch; }
details.more:last-of-type { border-bottom: 1px solid var(--rule); }
details.more > summary { cursor: pointer; font-weight: 650; list-style: none; display: flex; justify-content: space-between; gap: var(--s2); min-height: 44px; align-items: center; }
details.more > summary::-webkit-details-marker { display: none; }
details.more > summary::after { content: "+"; font-family: var(--font-math); font-size: 1.4rem; color: var(--text-3); transition: transform 200ms var(--ease-out); }
details.more[open] > summary::after { transform: rotate(45deg); }
details.more > *:not(summary) { margin-top: var(--s2); }

/* Prev/next */
.trick-pager { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s2); margin-top: var(--s6); }
.trick-pager a { display: grid; gap: 4px; padding: var(--s2) 0; border-top: 1px solid var(--rule-strong); text-decoration: none; }
.trick-pager a:hover .pager-title { text-decoration: underline; text-underline-offset: 3px; }
.trick-pager .pager-dir { font-size: 0.8rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--text-3); font-weight: 600; }
.trick-pager .pager-title { font-family: var(--font-display); font-size: 1.2rem; }
.trick-pager .next { text-align: right; grid-column: 2; }

/* ---------- Toast ---------- */
.toast-region { position: fixed; left: 50%; bottom: 20px; transform: translateX(-50%); z-index: 50; display: grid; gap: 8px; pointer-events: none; width: min(92vw, 440px); }
.toast { pointer-events: auto; background: var(--stage); color: var(--paper); border-radius: 10px; padding: 12px 14px; display: flex; gap: 12px; align-items: center; justify-content: space-between; box-shadow: 0 6px 24px rgba(0,0,0,0.25); font-size: 0.98rem; animation: toast-in 220ms var(--ease-out) both; }
.toast .btn { min-height: 36px; --btn-fg: var(--active); --btn-border: transparent; padding: 0 8px; }
@keyframes toast-in { from { opacity: 0; transform: translateY(8px); } }

/* ---------- Motion preferences ---------- */
@media (prefers-reduced-motion: reduce) {
  .card-inner { transition: transform 1ms linear; }
  .card-tilt { transition: none; }
  .secret.is-revealing { animation: fade-only 200ms ease both; }
  @keyframes fade-only { from { opacity: 0; } }
  .toast { animation: none; }
}

@media (max-width: 560px) {
  body { font-size: 1.0625rem; }
  .btn { white-space: normal; text-align: center; line-height: 1.2; padding-block: 8px; }
  .site-nav { gap: var(--s2); }
  .trick-pager { grid-template-columns: 1fr; }
  .trick-pager .next { grid-column: 1; text-align: left; }
  .stage { border-radius: 12px; margin-left: -8px; margin-right: -8px; }
}