/* ============================================================================
   Sliding Puzzle — style.css (Game 03, plan/games/03-sliding-puzzle.md §4)
   Mobile-first, one-thumb layout; the playing screen fits 360 px with the
   HUD visible and no scroll. Tiles are absolutely-positioned buttons moved
   via transform: translate transitions; the blank is simply a missing tile.
   Theme follows the site's `ai-quiz-theme` setting (resolved to
   [data-theme="dark"] / "light" by an inline script in index.html).
   ========================================================================== */

:root,
[data-theme='light'] {
  --bg-a: #e8e4f3;
  --bg-b: #d4c5e8;
  --card: #ffffff;
  --card-border: rgba(148, 163, 184, 0.35);
  --text: #1e293b;
  --muted: #64748b;
  --board: #94a3b8;
  --socket: #cbd5e1;
  --tile: #f8fafc;
  --tile-hover: #eef2ff;
  --primary-a: #2563eb;
  --primary-b: #4f46e5;
  --gold: #b45309;
  --gold-bg: #fef3c7;
  --shadow: 0 10px 30px rgba(30, 27, 75, 0.12);
}

[data-theme='dark'] {
  --bg-a: #1e1b4a;
  --bg-b: #3f1229;
  --card: #1e293b;
  --card-border: rgba(148, 163, 184, 0.18);
  --text: #f1f5f9;
  --muted: #94a3b8;
  --board: #475569;
  --socket: #334155;
  --tile: #16202f;
  --tile-hover: #1c2a3f;
  --primary-a: #3b82f6;
  --primary-b: #6366f1;
  --gold: #fbbf24;
  --gold-bg: rgba(251, 191, 36, 0.14);
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  font-family:
    ui-sans-serif,
    system-ui,
    -apple-system,
    'Segoe UI',
    Roboto,
    'Helvetica Neue',
    Arial,
    sans-serif;
  color: var(--text);
  background: linear-gradient(160deg, var(--bg-a), var(--bg-b)) fixed;
  -webkit-tap-highlight-color: transparent;
}

.app {
  min-height: 100vh;
  min-height: 100dvh;
  max-width: none; /* BUG-016 sweep: full-screen per owner request */
  margin: 0 auto;
  padding: 0.75rem 1rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.back-link {
  align-self: flex-start;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--muted);
  text-decoration: none;
  padding: 0.25rem 0.5rem;
  margin-left: -0.5rem;
  border-radius: 8px;
}

.back-link:hover,
.back-link:focus-visible {
  color: var(--text);
  background: var(--tile-hover);
}

.hidden {
  display: none !important;
}

/* Visually hidden but exposed to assistive tech (live region). */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ---- screens -------------------------------------------------------------- */

.screen {
  display: none;
  flex-direction: column;
  gap: 0.75rem;
  flex: 1;
  min-height: 0;
}

.screen--active {
  display: flex;
}

/* ---- menu ----------------------------------------------------------------- */

.menu-title {
  margin: 0.25rem 0 0;
  text-align: center;
  font-size: clamp(1.6rem, 7vw, 2.1rem);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.tagline {
  margin: 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--muted);
}

.card {
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 16px;
  padding: 1rem;
  box-shadow: var(--shadow);
}

.card h2 {
  margin: 0 0 0.5rem;
  font-size: 0.8125rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}

/* segmented control (Numbers / Picture) — the picked option is highlighted */

.segmented {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 1fr;
  gap: 4px;
  background: var(--tile);
  border: 1px solid var(--card-border);
  border-radius: 12px;
  padding: 4px;
}

.segmented button {
  border: 0;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.5rem 0.25rem;
  border-radius: 9px;
  cursor: pointer;
  touch-action: manipulation;
}

.segmented button[aria-checked='true'] {
  background: var(--card);
  color: var(--text);
  box-shadow: 0 1px 4px rgba(15, 23, 42, 0.18);
}

/* daily challenge button: secondary full-width entry under Play */

button.daily {
  border: 2px solid var(--card-border);
  border-radius: 14px;
  padding: 0.65rem 1rem;
  font: inherit;
  color: var(--text);
  background: var(--card);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
  box-shadow: var(--shadow);
  transition:
    transform 0.12s ease,
    border-color 0.12s ease;
}

button.daily:hover,
button.daily:focus-visible {
  border-color: var(--primary-a);
  transform: scale(0.99);
}

.daily-title {
  font-size: 1rem;
  font-weight: 700;
}

.daily-sub {
  font-size: 0.75rem;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

/* size picker: three cards, each carrying its own personal record */

.size-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
}

.size-card {
  border: 2px solid var(--card-border);
  border-radius: 14px;
  background: var(--tile);
  color: var(--text);
  font: inherit;
  padding: 0.75rem 0.25rem 0.625rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
  cursor: pointer;
  transition:
    border-color 0.12s ease,
    background 0.12s ease;
}

.size-card:hover,
.size-card:focus-visible {
  background: var(--tile-hover);
}

.size-card[aria-checked='true'] {
  border-color: var(--primary-a);
  background: var(--tile-hover);
}

.size-card .grid-label {
  font-size: 1.25rem;
  font-weight: 800;
}

.size-card .best {
  font-size: 0.6875rem;
  color: var(--muted);
  text-align: center;
  line-height: 1.3;
}

.toggle-row {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  margin-top: 0.875rem;
  font-size: 0.875rem;
  cursor: pointer;
}

.toggle-row input {
  width: 1.125rem;
  height: 1.125rem;
  accent-color: var(--primary-a);
  flex-shrink: 0;
}

/* buttons */

button.primary {
  border: 0;
  border-radius: 14px;
  padding: 0.875rem 1rem;
  font: inherit;
  font-size: 1rem;
  font-weight: 700;
  color: #fff;
  background: linear-gradient(135deg, var(--primary-a), var(--primary-b));
  cursor: pointer;
  box-shadow: 0 6px 18px rgba(37, 99, 235, 0.35);
  transition:
    transform 0.12s ease,
    box-shadow 0.12s ease,
    filter 0.12s ease;
}

button.primary:hover:not(:disabled) {
  filter: brightness(1.06);
}

button.primary:active:not(:disabled) {
  transform: scale(0.98);
}

button.ghost {
  border: 1px solid var(--card-border);
  border-radius: 12px;
  padding: 0.625rem 0.875rem;
  font: inherit;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text);
  background: var(--card);
  cursor: pointer;
  touch-action: manipulation;
}

button.ghost:hover:not(:disabled),
button.ghost:focus-visible {
  background: var(--tile-hover);
}

button:focus-visible,
a:focus-visible {
  outline: 3px solid var(--primary-a);
  outline-offset: 2px;
}

/* ---- playing screen --------------------------------------------------------- */

/* one compact centered strip — menu, HUD and pause sit together instead of
   being pinned to the screen edges with large gaps between them */

.topbar {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  flex-wrap: wrap; /* safety on very narrow screens */
}

.topbar .ghost {
  padding: 0.4rem 0.65rem;
}

.hud {
  display: flex;
  justify-content: center;
  gap: 0.4rem;
}

.chip {
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 999px;
  padding: 0.4rem 0.7rem;
  font-size: 0.875rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.chip .chip-icon {
  margin-right: 0.3rem;
}

.actions {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
}

.actions .ghost {
  padding: 0.5rem 0.85rem;
}

/* the board: plan §4 sizes it min(92vw, 60dvh); tiles are positioned by
   transform translate(±cell), so --x/--y are plain cell coordinates */

/* the play cluster: HUD, board and action buttons hug together as one
   centered group — on tall/desktop windows nothing stretches toward the
   screen edges (no orphaned thumbnail, no buttons stranded at the bottom) */

#screen-playing {
  justify-content: center;
}

.board-wrap {
  position: relative;
  flex: 0 0 auto;
  align-self: center; /* shrink to the board's exact box — overlays cover it fully */
  display: flex;
  align-items: center;
  justify-content: center;
}

.board-shell {
  position: relative; /* anchors the corner preview to the board itself */
  flex: 0 0 auto;
}

.board {
  --n: 3;
  --gap: 0px; /* BUG-017: tiles sit flush — no visible gap between moving blocks */
  position: relative;
  width: min(92vw, 72dvh); /* BUG-016 sweep: fills the viewport height */
  max-width: none;
  aspect-ratio: 1;
  background: var(--socket);
  border: 1px solid var(--board);
  border-radius: 18px;
  touch-action: manipulation;
}

.tile {
  position: absolute;
  top: 0;
  left: 0;
  width: calc(100% / var(--n));
  height: calc(100% / var(--n));
  border: var(--gap) solid transparent;
  background-clip: padding-box; /* the border is the gutter between tiles */
  background-color: var(--tile);
  border-radius: 0; /* BUG-017: flush tiles — rounded corners would leave notches */
  color: var(--text);
  font: inherit;
  font-weight: 800;
  font-size: calc(min(92vw, 60vh) / var(--n) * 0.36);
  font-size: calc(min(92vw, 60dvh) / var(--n) * 0.36);
  font-variant-numeric: tabular-nums;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
  padding: 0;
  transform: translate(calc(var(--x, 0) * 100%), calc(var(--y, 0) * 100%));
  transition: transform 180ms ease;
}

/* BUG-030: no per-tile hover tint — every block must look fully adjusted
   at all times (a lingering tint read as an "active" unadjusted block). */

.tile:focus-visible {
  outline: 3px solid var(--primary-a);
  outline-offset: -6px;
  z-index: 1;
}

/* ---- picture mode (plan P3): each tile owns one fixed slice of the image */

/* corner thumbnail of the target picture, with the n×n grid overlaid so
   slices can be matched to cells; tap to enlarge */

.pic-preview {
  position: static; /* BUG-017: reference sits outside the sliding container */
  display: block;
  margin: 0 auto 0.6rem;
  width: clamp(48px, 15vw, 68px);
  aspect-ratio: 1;
  padding: 0;
  border: 2px solid var(--card-border);
  border-radius: 12px;
  background-size: 100% 100%;
  box-shadow: var(--shadow);
  cursor: zoom-in;
  z-index: 2;
  --n: 3;
}

.pic-preview::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 10px;
  background-image:
    repeating-linear-gradient(
      90deg,
      rgba(255, 255, 255, 0.5) 0 1px,
      transparent 1px calc(100% / var(--n))
    ),
    repeating-linear-gradient(
      0deg,
      rgba(255, 255, 255, 0.5) 0 1px,
      transparent 1px calc(100% / var(--n))
    );
  pointer-events: none;
}

.overlay--preview {
  /* Fallback first: without color-mix the scrim must still be visible. */
  background: rgba(15, 23, 42, 0.72);
  background: color-mix(in srgb, var(--bg-a) 72%, transparent);
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
  z-index: 3;
}

.preview-card {
  width: 100%;
  max-width: 19rem;
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 18px;
  box-shadow: var(--shadow);
  padding: 0.85rem;
  text-align: center;
}

.preview-image {
  width: 100%;
  aspect-ratio: 1;
  border: 1px solid var(--card-border);
  border-radius: 12px;
  background-size: 100% 100%;
}

.preview-card .overlay-sub {
  margin: 0.6rem 0 0.75rem;
}

.preview-card .ghost {
  width: 100%;
}

.row-label {
  margin-top: 0.875rem;
}

.tile-num {
  pointer-events: none;
}

.board--picture .tile {
  background-color: transparent;
}

/* BUG-030: picture-mode tiles also stay uniform — no hover brightness flash. */

.board--picture .tile-num {
  display: none;
}

/* Peek shows a small readable number pill over each slice */

.board--picture.board--peek .tile-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.9em;
  padding: 0.08em 0.3em;
  border-radius: 0.6em;
  background: rgba(15, 23, 42, 0.66);
  color: #fff;
  font-size: calc(min(92vw, 60vh) / var(--n) * 0.2);
  font-size: calc(min(92vw, 60dvh) / var(--n) * 0.2);
}

/* on win, the blank receives its slice back and the picture completes */

.tile--ghost {
  pointer-events: none;
  cursor: default;
  animation: ghost-in 0.45s ease-out;
}

@keyframes ghost-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

/* wrong-tile shake (plan §2). Animates the `translate` property so it
   composes with the positioning transform instead of clobbering it. */

.tile--shake {
  animation: tile-shake 0.3s ease;
}

@keyframes tile-shake {
  0%,
  100% {
    translate: 0 0;
  }
  20% {
    translate: -4% 0;
  }
  40% {
    translate: 4% 0;
  }
  60% {
    translate: -3% 0;
  }
  80% {
    translate: 3% 0;
  }
}

/* ---- pause overlay: opaque, the board must be hidden (plan §7.3) ---------- */

.overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem;
  border-radius: 18px;
}

.overlay--pause {
  background: var(--bg-a); /* fully opaque — no sneaking moves */
  border: 1px solid var(--board);
}

.overlay--win {
  /* Fallback first: without color-mix the scrim must still be visible. */
  background: rgba(15, 23, 42, 0.55);
  background: color-mix(in srgb, var(--bg-a) 55%, transparent);
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
}

.overlay-card {
  width: 100%;
  max-width: 19rem;
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 18px;
  box-shadow: var(--shadow);
  padding: 1.25rem 1rem;
  text-align: center;
}

.overlay-emoji {
  font-size: 2rem;
  line-height: 1;
}

.overlay-title {
  margin: 0.375rem 0 0.25rem;
  font-size: 1.5rem;
  font-weight: 800;
}

.overlay-sub {
  margin: 0 0 1rem;
  font-size: 0.875rem;
  color: var(--muted);
}

.win-stats {
  font-size: 1.125rem;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  margin: 0.25rem 0 0.5rem;
}

.badges {
  display: flex;
  justify-content: center;
  gap: 0.375rem;
  margin-bottom: 0.5rem;
}

.badge-new {
  font-size: 0.6875rem;
  font-weight: 800;
  letter-spacing: 0.04em;
  color: var(--gold);
  background: var(--gold-bg);
  border: 1px solid currentColor;
  border-radius: 999px;
  padding: 0.2rem 0.6rem;
}

.overlay-actions {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.overlay-actions .ghost-row {
  display: flex;
  gap: 0.5rem;
}

.overlay-actions .ghost-row > button {
  flex: 1;
}

/* ---- toast ------------------------------------------------------------------ */

.toast {
  position: fixed;
  left: 50%;
  bottom: 1.25rem;
  transform: translate(-50%, 200%);
  /* parked fully out of sight — the % translate resolves against the content
     box, so the padded pill otherwise peeks above the bottom edge */
  opacity: 0;
  background: var(--text);
  color: var(--card);
  font-size: 0.8125rem;
  font-weight: 600;
  padding: 0.5rem 0.9rem;
  border-radius: 999px;
  transition:
    transform 0.25s ease,
    opacity 0.25s ease;
  pointer-events: none;
  z-index: 10;
}

.toast--in {
  transform: translate(-50%, 0);
  opacity: 1;
}

/* ---- small viewports ----------------------------------------------------------- */

@media (max-height: 560px) {
  .app {
    gap: 0.5rem;
  }

  .menu-title {
    font-size: 1.4rem;
  }

  .card {
    padding: 0.75rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .tile {
    transition: none;
  }

  .tile--shake,
  .tile--ghost {
    animation: none;
  }

  button.primary,
  button.ghost,
  button.daily,
  .size-card,
  .toast {
    transition: none;
  }
}

/* ---- one-swap-away nudge (suggestion 03 item 2) ---------------------------- */

.nudge {
  position: absolute;
  left: 50%;
  bottom: -2.4rem;
  transform: translateX(-50%);
  background: var(--card, #fff);
  color: var(--text, #1e293b);
  border: 1px solid var(--card-border, #cbd5e1);
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.85rem;
  padding: 0.4rem 0.9rem;
  white-space: nowrap;
  box-shadow: 0 6px 18px rgb(0 0 0 / 0.18);
  z-index: 5;
}

.nudge[hidden] {
  display: none;
}