/* ═══════════════════════════════════════════════════════════════════════════
   Chess — style.css
   Design system: deep slate bg, walnut-cream board, gold accents
   Signature: king check pulse + material bar micro-detail
   ═══════════════════════════════════════════════════════════════════════════ */

/* ─── Reset & Box Model ──────────────────────────────────────────────────── */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* ─── Design Tokens ──────────────────────────────────────────────────────── */

:root {
  /* Board */
  --sq-light: #ebecd0;
  --sq-dark: #779556;
  --board-border: #312e2b;
  --board-shadow: rgba(0, 0, 0, 0.15);

  /* Square highlights */
  --hl-selected: rgba(255, 255, 51, 0.5);
  --hl-last: rgba(255, 255, 51, 0.5);
  --hl-check: rgba(235, 97, 80, 0.8);
  --hl-legal-dot: rgba(0, 0, 0, 0.15);
  --hl-legal-ring: rgba(0, 0, 0, 0.15);

  /* App chrome */
  --bg: #edebe9;
  --surface-1: #ffffff; /* cards, panels */
  --surface-2: #f1f1f1; /* buttons, inputs */
  --surface-3: #e3e3e3; /* hover states */
  --border: #d3d3d3;
  --border-accent: #81b64c;

  /* Typography */
  --text-primary: #312e2b;
  --text-secondary: #8b8987;
  --text-accent: #81b64c;
  --text-danger: #e05555;

  /* Piece colors */
  --piece-white: #f8f8f8;
  --piece-black: #312e2b;

  /* Sizing — board square size drives layout */
  --sq: min(10.8vw, calc(12.5vh - 30px), 78px);
  --board-size: calc(var(--sq) * 8);
  --coord-gutter: 20px;

  /* Radius */
  --r-sm: 6px;
  --r-md: 10px;
  --r-lg: 14px;

  /* Transitions */
  --t-fast: 0.12s ease;
  --t-mid: 0.2s ease;
}

/* ─── Base ───────────────────────────────────────────────────────────────── */

html,
body {
  height: 100%;
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ─── Header ─────────────────────────────────────────────────────────────── */

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  height: 52px;
  background: var(--surface-1);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  position: sticky;
  top: 0;
  z-index: 50;
}

.logo {
  display: flex;
  align-items: center;
  gap: 9px;
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  color: var(--text-primary);
  user-select: none;
}

.logo-icon {
  font-size: 1.5rem;
  color: var(--text-accent);
  line-height: 1;
}

.header-actions {
  display: flex;
  gap: 7px;
  align-items: center;
}

/* ─── Buttons ────────────────────────────────────────────────────────────── */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-primary);
  padding: 7px 13px;
  border-radius: var(--r-sm);
  cursor: pointer;
  font-size: 0.81rem;
  font-weight: 500;
  letter-spacing: 0.01em;
  line-height: 1;
  transition:
    background var(--t-fast),
    border-color var(--t-fast),
    color var(--t-fast);
  white-space: nowrap;
  user-select: none;
}

.btn:hover {
  background: var(--surface-3);
  border-color: var(--border-accent);
  color: var(--text-accent);
}

.btn:active {
  transform: scale(0.97);
}

.btn .btn-icon {
  font-size: 0.95rem;
  line-height: 1;
  opacity: 0.85;
}

/* ─── Main Layout ────────────────────────────────────────────────────────── */

.app-main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 24px 20px 32px;
  gap: 0;
}

.game-layout {
  display: flex;
  gap: 18px;
  align-items: flex-start;
  width: 100%;
  max-width: calc(var(--board-size) + var(--coord-gutter) + 18px + 240px);
  justify-content: center;
}

/* ─── Board Column ───────────────────────────────────────────────────────── */

.board-column {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  flex-shrink: 0;
}

/* ─── Player Bar ─────────────────────────────────────────────────────────── */

.player-bar {
  width: calc(var(--board-size) + var(--coord-gutter));
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 7px 10px 7px 8px;
  background: var(--surface-1);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  transition:
    border-color var(--t-mid),
    box-shadow var(--t-mid);
}

.player-bar.top {
  margin-bottom: 5px;
}
.player-bar.bottom {
  margin-top: 5px;
}

.player-bar.active-turn {
  border-color: var(--border-accent);
  box-shadow: 0 0 0 1px rgba(201, 168, 76, 0.22);
}

.player-left {
  display: flex;
  align-items: center;
  gap: 9px;
  min-width: 0;
}

.player-avatar {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.05rem;
  flex-shrink: 0;
}

.player-avatar.white-av {
  background: #f8f8f8;
  color: #312e2b;
  border: 1px solid var(--border);
}

.player-avatar.black-av {
  background: #312e2b;
  color: #f8f8f8;
  border: 1px solid var(--border);
}

.player-meta {
  display: flex;
  flex-direction: column;
  gap: 1px;
  min-width: 0;
}

.player-name {
  font-size: 0.87rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.2;
}

.captured-pieces {
  font-size: 0.88rem;
  letter-spacing: -1.5px;
  color: var(--text-secondary);
  min-height: 16px;
  line-height: 1.2;
}

.player-right {
  display: flex;
  align-items: center;
  gap: 9px;
  flex-shrink: 0;
}

.material-diff {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-accent);
  min-width: 20px;
  text-align: right;
  letter-spacing: 0.02em;
}

.turn-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--text-accent);
  animation: pulse-dot 1.3s ease-in-out infinite;
  flex-shrink: 0;
  transition: opacity var(--t-fast);
}

.turn-dot.hidden {
  opacity: 0;
  animation: none;
}

@keyframes pulse-dot {
  0%,
  100% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0.3;
    transform: scale(0.65);
  }
}

/* ─── Board Wrapper ──────────────────────────────────────────────────────── */

.board-wrapper {
  position: relative;
  display: inline-block;
}

/* Rank labels (left side) */
.coords-col {
  position: absolute;
  left: 0;
  top: 0;
  width: var(--coord-gutter);
  height: var(--board-size);
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  align-items: center;
  pointer-events: none;
  z-index: 2;
}

/* File labels (bottom) */
.coords-row {
  position: absolute;
  bottom: 0;
  left: var(--coord-gutter);
  width: var(--board-size);
  height: var(--coord-gutter);
  display: flex;
  flex-direction: row;
  justify-content: space-around;
  align-items: center;
  pointer-events: none;
  z-index: 2;
}

.coord-label {
  font-size: 0.65rem;
  font-weight: 700;
  color: var(--coord-color, #555555);
  line-height: 1;
  user-select: none;
  text-align: center;
  opacity: 0.85;
  text-shadow: 0 0 2px rgba(255, 255, 255, 0.4);
}

/* ─── Board ──────────────────────────────────────────────────────────────── */

#board {
  display: grid;
  grid-template-columns: repeat(8, var(--sq));
  grid-template-rows: repeat(8, var(--sq));
  border: 3px solid var(--board-border);
  border-radius: 3px;
  box-shadow:
    0 0 0 5px var(--board-shadow),
    0 18px 56px rgba(0, 0, 0, 0.75);
  margin-left: var(--coord-gutter);
  user-select: none;
  cursor: default;
  position: relative;
  perspective: 1000px;
}

/* ─── Squares ────────────────────────────────────────────────────────────── */

.sq {
  width: var(--sq);
  height: var(--sq);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  cursor: pointer;
  transition: background-color 0.07s;
}

.sq.light {
  background: var(--sq-light);
}
.sq.dark {
  background: var(--sq-dark);
}

/* Last-move highlight — must come before selected so selected wins */
.sq.sq-last-from,
.sq.sq-last-to {
  background: var(--hl-last) !important;
}

/* Selected square */
.sq.sq-selected {
  background: var(--hl-selected) !important;
}

/* Check — king square pulses */
.sq.sq-check {
  background: var(--hl-check);
  animation: check-pulse 0.85s ease-in-out infinite;
}

@keyframes check-pulse {
  0%,
  100% {
    background: var(--hl-check);
  }
  50% {
    background: rgba(220, 40, 40, 0.3);
  }
}

/* Legal move dot (empty target) */
.sq.sq-legal::after {
  content: "";
  position: absolute;
  width: 30%;
  height: 30%;
  border-radius: 50%;
  background: var(--hl-legal-dot);
  pointer-events: none;
  z-index: 2;
}

/* Legal capture ring (occupied target) */
.sq.sq-legal-capture::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 50%;
  box-shadow: inset 0 0 0 5px var(--hl-legal-ring);
  pointer-events: none;
  z-index: 2;
}

/* ─── Pieces ─────────────────────────────────────────────────────────────── */

.piece {
  font-size: calc(var(--sq) * 0.75);
  line-height: 1;
  position: relative;
  z-index: 3;
  pointer-events: none;
  transition: transform 0.1s ease;
}

.piece.white-piece {
  color: var(--piece-white);
  filter: drop-shadow(0 0 1px rgba(100, 100, 100, 0.8))
    drop-shadow(0 1px 3px rgba(0, 0, 0, 0.65));
}

.piece.black-piece {
  color: var(--piece-black);
  filter: drop-shadow(0 1px 1px rgba(255, 255, 255, 0.12))
    drop-shadow(0 1px 4px rgba(0, 0, 0, 0.85));
}

.sq:hover .piece {
  transform: scale(1.07) translateY(-1px);
}

/* ─── Sidebar ────────────────────────────────────────────────────────────── */

.sidebar {
  width: 236px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  flex-shrink: 0;
  /* Align sidebar top with board top (player-bar height + gap) */
  margin-top: calc(
    30px + 5px + 3px
  ); /* approx player-bar height + gap + border */
}

/* ─── Panel Card ─────────────────────────────────────────────────────────── */

.panel-card {
  background: var(--surface-1);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  overflow: hidden;
}

.panel-header {
  padding: 9px 14px 8px;
  border-bottom: 1px solid var(--border);
  font-size: 0.66rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-secondary);
}

.panel-body {
  padding: 12px 14px;
}

/* ─── Status Card ────────────────────────────────────────────────────────── */

.status-value {
  font-size: 0.97rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.3;
}

.status-value.in-check {
  color: var(--text-danger);
}
.status-value.game-over {
  color: var(--text-accent);
}

/* ─── Game-Over Banner ───────────────────────────────────────────────────── */

#gameover-banner {
  display: none;
  background: linear-gradient(140deg, var(--surface-1), var(--surface-2));
  border: 1.5px solid var(--border-accent);
  border-radius: var(--r-md);
  padding: 14px 16px;
  text-align: center;
}

#gameover-banner.visible {
  display: block;
}

.gameover-title {
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-accent);
  letter-spacing: 0.03em;
  margin-bottom: 3px;
}

.gameover-subtitle {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* ─── Move History ───────────────────────────────────────────────────────── */

.move-history-card {
  display: flex;
  flex-direction: column;
  flex: 1;
  min-height: 180px;
  max-height: 480px;
}

#move-list {
  overflow-y: auto;
  flex: 1;
  padding: 6px 4px;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

#move-list::-webkit-scrollbar {
  width: 3px;
}
#move-list::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 2px;
}

.move-row {
  display: grid;
  grid-template-columns: 26px 1fr 1fr;
  border-radius: var(--r-sm);
  overflow: hidden;
}

.move-row:nth-child(odd) {
  background: rgba(255, 255, 255, 0.025);
}

.move-num {
  padding: 4px 4px 4px 8px;
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--text-secondary);
  line-height: 1.7;
  font-variant-numeric: tabular-nums;
}

.move-cell {
  padding: 4px 6px;
  font-size: 0.79rem;
  font-family: "Courier New", "Consolas", monospace;
  color: var(--text-primary);
  line-height: 1.7;
  border-radius: 3px;
  cursor: pointer;
  transition: background var(--t-fast);
}

.move-cell:hover {
  background: var(--surface-3);
}

.move-cell.latest {
  background: rgba(201, 168, 76, 0.16);
  color: var(--text-accent);
  font-weight: 700;
}

/* ─── Promotion Overlay ──────────────────────────────────────────────────── */

#promotion-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.78);
  z-index: 200;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(3px);
}

#promotion-overlay.visible {
  display: flex;
}

.promotion-panel {
  background: var(--surface-1);
  border: 2px solid var(--border-accent);
  border-radius: var(--r-lg);
  padding: 24px 28px;
  text-align: center;
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.85);
  animation: panel-in 0.18s ease;
}

@keyframes panel-in {
  from {
    opacity: 0;
    transform: scale(0.92) translateY(-8px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.promotion-title {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.promotion-choices {
  display: flex;
  gap: 10px;
  justify-content: center;
}

.promo-btn {
  width: 72px;
  height: 80px;
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  border-radius: var(--r-md);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  transition:
    background var(--t-fast),
    border-color var(--t-fast),
    transform 0.12s;
}

.promo-btn:hover {
  background: var(--surface-3);
  border-color: var(--border-accent);
  transform: translateY(-2px);
}

.promo-glyph {
  font-size: 2.4rem;
  line-height: 1;
  display: block;
}

/* Re-use piece color classes for promotion glyphs */
.promo-glyph.white-piece {
  color: var(--piece-white);
  filter: drop-shadow(0 0 1px rgba(100, 100, 100, 0.8))
    drop-shadow(0 1px 3px rgba(0, 0, 0, 0.65));
}

.promo-glyph.black-piece {
  color: var(--piece-black);
  filter: drop-shadow(0 1px 1px rgba(255, 255, 255, 0.12))
    drop-shadow(0 1px 4px rgba(0, 0, 0, 0.85));
}

.promo-label {
  font-size: 0.65rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ─── Toast ──────────────────────────────────────────────────────────────── */

#toast {
  position: fixed;
  bottom: 28px;
  left: 50%;
  transform: translateX(-50%) translateY(12px);
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-primary);
  padding: 9px 18px;
  border-radius: 100px;
  font-size: 0.82rem;
  font-weight: 500;
  opacity: 0;
  pointer-events: none;
  transition:
    opacity 0.2s ease,
    transform 0.2s ease;
  z-index: 300;
  white-space: nowrap;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
}

#toast.visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* ─── Move Navigation Controls ───────────────────────────────────────────── */

.move-nav-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 8px;
  border-bottom: 1px solid var(--border);
}

.move-nav-btn {
  width: 32px;
  height: 32px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  transition:
    background var(--t-fast),
    border-color var(--t-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.move-nav-btn:hover {
  background: var(--surface-3);
  border-color: var(--border-accent);
}

.move-nav-btn:active {
  transform: scale(0.95);
}

.move-counter {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-secondary);
  min-width: 40px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

.move-cell.current {
  background: var(--hl-selected);
  color: var(--text-primary);
  font-weight: 700;
  border-radius: 4px;
}

/* ─── Statistics Card ────────────────────────────────────────────────────── */

.stats-card {
  display: flex;
  flex-direction: column;
}

.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  padding: 12px;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 8px;
  background: var(--surface-2);
  border-radius: var(--r-sm);
  border: 1px solid var(--border);
}

.stat-label {
  font-size: 0.65rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.stat-value {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--text-accent);
  font-variant-numeric: tabular-nums;
}

/* ─── Modal Dialogs ──────────────────────────────────────────────────────── */

.modal {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.8);
  z-index: 250;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(4px);
}

.modal.visible {
  display: flex;
}

.modal-content {
  background: var(--surface-1);
  border: 1.5px solid var(--border);
  border-radius: var(--r-lg);
  max-width: 480px;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: 0 24px 80px rgba(0, 0, 0, 0.9);
  animation: slide-up 0.24s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes slide-up {
  from {
    opacity: 0;
    transform: translateY(24px) scale(0.96);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 18px;
  border-bottom: 1px solid var(--border);
}

.modal-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: 0.01em;
}

.modal-close {
  width: 28px;
  height: 28px;
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-secondary);
  cursor: pointer;
  border-radius: var(--r-sm);
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition:
    background var(--t-fast),
    color var(--t-fast);
}

.modal-close:hover {
  background: var(--surface-2);
  color: var(--text-primary);
}

/* ─── Theme Selector ─────────────────────────────────────────────────────── */

.theme-options {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
  padding: 16px 18px;
}

.theme-option {
  height: 80px;
  border: 2px solid var(--border);
  border-radius: var(--r-md);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  padding: 8px;
  color: var(--text-primary);
  transition:
    border-color var(--t-fast),
    transform 0.12s;
}

.theme-option:hover {
  transform: translateY(-2px);
}

.theme-option.active {
  border-color: var(--text-accent);
  box-shadow: 0 0 0 2px rgba(201, 168, 76, 0.3);
}

/* ─── Settings Options ───────────────────────────────────────────────────── */

.settings-options {
  padding: 16px 18px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.setting-item {
  display: flex;
  align-items: center;
  gap: 10px;
}

.setting-item label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--text-primary);
  flex: 1;
}

.setting-item input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
  accent-color: var(--text-accent);
}

.setting-item select {
  background: var(--surface-2);
  color: var(--text-primary);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  padding: 6px 8px;
  font-size: 0.85rem;
  cursor: pointer;
  margin-left: auto;
}

#btn-clear-storage {
  width: 100%;
  background: var(--surface-2);
  color: var(--text-danger);
}

#btn-clear-storage:hover {
  background: rgba(224, 85, 85, 0.15);
}

.btn-secondary {
  background: var(--surface-2);
  border-color: var(--border);
  color: var(--text-primary);
}

.btn-secondary:hover {
  background: var(--surface-3);
}

/* ─── Shortcuts Help ─────────────────────────────────────────────────────── */

.shortcuts-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 16px 18px;
}

.shortcut-item {
  display: grid;
  grid-template-columns: 70px 1fr;
  gap: 14px;
  align-items: center;
  padding: 10px;
  background: var(--surface-2);
  border-radius: var(--r-sm);
  border: 1px solid var(--border);
}

.shortcut-key {
  font-family: "Courier New", "Consolas", monospace;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-accent);
  padding: 6px 8px;
  background: rgba(201, 168, 76, 0.12);
  border-radius: 3px;
  text-align: center;
  border: 1px solid rgba(201, 168, 76, 0.25);
}

.shortcut-desc {
  font-size: 0.85rem;
  color: var(--text-primary);
}

/* ─── Dark Mode ──────────────────────────────────────────────────────────── */

:root.dark-mode {
  --board-shadow: rgba(0, 0, 0, 0.4);

  --bg: #312e2b;
  --surface-1: #262421;
  --surface-2: #3c3a38;
  --surface-3: #4b4845;
  --border: #403d39;
  --border-accent: #81b64c;

  --text-primary: #ffffff;
  --text-secondary: #c3c3c3;
  --text-accent: #81b64c;
  --text-danger: #f85149;

  --piece-white: #f8f8f8;
  --piece-black: #111111;
}

/* ─── Animations & Transitions ──────────────────────────────────────────── */

/* Smooth piece movement */
@keyframes piece-move {
  from {
    transform: translate(0, 0);
  }
  to {
    transform: translate(0, 0);
  }
}

/* Board flip animation */
@keyframes board-flip {
  from {
    transform: rotateY(0deg) rotateZ(0deg);
    opacity: 1;
  }
  50% {
    opacity: 0.85;
  }
  to {
    transform: rotateY(180deg) rotateZ(0deg);
    opacity: 1;
  }
}

/* Enable animations when setting allows */
body:not(.animations-disabled) {
  --animations: 1;
}

/* Legal move indicators with better visibility */
.sq.sq-legal::after,
.sq.sq-legal-capture::after {
  animation: legal-pulse 1.2s ease-in-out infinite;
}

@keyframes legal-pulse {
  0%,
  100% {
    opacity: 1;
  }
  50% {
    opacity: 0.6;
  }
}

/* ─── Responsive — Tablet ────────────────────────────────────────────────── */

@media (max-width: 740px) {
  :root {
    --sq: min(11vw, 66px);
    --coord-gutter: 18px;
  }

  .app-main {
    padding: 14px 10px 24px;
  }

  .game-layout {
    flex-direction: column;
    align-items: center;
    gap: 14px;
  }

  .sidebar {
    width: calc(var(--board-size) + var(--coord-gutter));
    margin-top: 0;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }

  .status-card {
    grid-column: 1 / -1;
  }
  #gameover-banner {
    grid-column: 1 / -1;
  }
  .move-history-card {
    grid-column: 1 / -1;
    max-height: 160px;
    min-height: 120px;
  }

  .stats-card {
    grid-column: 1 / -1;
  }

  .modal-content {
    width: 90vw;
    max-width: none;
  }

  .theme-options {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ─── Responsive — Mobile ────────────────────────────────────────────────── */

@media (max-width: 480px) {
  :root {
    --sq: calc((100vw - 44px) / 8);
    --coord-gutter: 14px;
  }

  .app-header {
    padding: 0 12px;
    height: 46px;
    gap: 6px;
  }

  .logo {
    gap: 6px;
    font-size: 1rem;
  }

  .logo-icon {
    font-size: 1.2rem;
  }

  .btn {
    padding: 5px 8px;
    font-size: 0.72rem;
    flex-shrink: 0;
  }

  .btn-icon {
    display: inline;
    font-size: 0.85rem;
    opacity: 0.7;
  }

  .header-actions {
    gap: 3px;
    overflow-x: auto;
  }

  .app-main {
    padding: 12px 8px 20px;
  }

  .player-bar {
    padding: 6px 8px;
    font-size: 0.9rem;
  }

  .player-avatar {
    width: 28px;
    height: 28px;
    font-size: 0.9rem;
  }

  .player-name {
    font-size: 0.8rem;
  }

  .captured-pieces {
    font-size: 0.75rem;
  }

  .sidebar {
    grid-template-columns: 1fr;
    width: 100%;
  }

  .move-history-card {
    max-height: 140px;
  }

  .stats-grid {
    grid-template-columns: 1fr 1fr;
    gap: 8px;
    padding: 10px;
  }

  .stat-item {
    padding: 6px;
  }

  .stat-value {
    font-size: 0.95rem;
  }

  .modal-content {
    width: 95vw;
    max-height: 90vh;
    border-radius: var(--r-md);
  }

  .modal-header {
    padding: 14px 14px;
  }

  .modal-title {
    font-size: 0.9rem;
  }

  .theme-options {
    grid-template-columns: 1fr 1fr;
    padding: 12px 14px;
  }

  .theme-option {
    height: 60px;
    font-size: 0.75rem;
  }

  .settings-options {
    padding: 12px 14px;
    gap: 12px;
  }

  .setting-item label {
    font-size: 0.85rem;
  }

  .shortcuts-list {
    gap: 8px;
    padding: 12px 14px;
  }

  .shortcut-item {
    grid-template-columns: 60px 1fr;
    gap: 10px;
    padding: 8px;
  }

  .shortcut-key {
    font-size: 0.75rem;
    padding: 4px 6px;
  }

  .shortcut-desc {
    font-size: 0.8rem;
  }

  .move-nav-controls {
    gap: 6px;
    padding: 6px;
  }

  .move-nav-btn {
    width: 28px;
    height: 28px;
    font-size: 0.75rem;
  }

  .move-counter {
    font-size: 0.7rem;
  }
}

/* ─── Small Mobile (iPhone SE) ────────────────────────────────────────────– */

@media (max-width: 375px) {
  :root {
    --sq: calc((100vw - 32px) / 8);
    --coord-gutter: 12px;
  }

  .app-header {
    height: 44px;
  }

  .logo span {
    display: none;
  }

  .btn {
    padding: 4px 6px;
    font-size: 0.65rem;
  }

  .sidebar {
    gap: 10px;
  }
}

/* ─── Reduced Motion ─────────────────────────────────────────────────────── */

@media (prefers-reduced-motion: reduce) {
  .turn-dot {
    animation: none;
    opacity: 1;
  }
  .sq.sq-check {
    animation: none;
  }
  .panel-card,
  .btn,
  .sq,
  .piece {
    transition: none;
  }
  .move-cell {
    transition: none;
  }
  .modal-content {
    animation: none;
  }
  .sq.sq-legal::after,
  .sq.sq-legal-capture::after {
    animation: none;
  }
}