:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-2: #273449;
  --border: rgba(148, 163, 184, 0.16);
  --text: #e2e8f0;
  --muted: #94a3b8;
  --accent: #f59e0b;
  --accent-ink: #1a1203;
  --danger: #ef4444;
  --radius: 12px;
  --shadow: 0 10px 30px rgba(2, 6, 23, 0.45);
  --ease: 180ms ease;
  --light-sq: #dce3ec;
  --dark-sq: #7b8ea8;
  --board-size: min(92vw, 560px);
  --sq: calc(var(--board-size) / 8);
  --piece-font: "Segoe UI Symbol", "Noto Sans Symbols 2", "Noto Sans Symbols", "Apple Symbols", "DejaVu Sans", "Arial Unicode MS", sans-serif;
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  background: radial-gradient(1200px 600px at 50% -200px, #1b2a47 0%, var(--bg) 60%) var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 15px;
  line-height: 1.45;
  overflow-x: hidden;
}

h1,
h2 {
  margin: 0;
}

.muted {
  color: var(--muted);
}

.offscreen {
  position: fixed;
  left: -9999px;
  top: 0;
  opacity: 0;
}

/* Header */
.topbar {
  width: 100%;
  max-width: 920px;
  margin: 0 auto;
  padding: 12px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
}

.logo {
  width: 34px;
  height: 34px;
  flex: none;
  filter: drop-shadow(0 4px 10px rgba(245, 158, 11, 0.25));
}

.brand h1 {
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: 0.01em;
}

.topbar-actions {
  display: flex;
  gap: 8px;
}

/* Buttons */
.btn {
  min-height: 42px;
  padding: 0 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 2px 6px rgba(2, 6, 23, 0.25);
  transition: background var(--ease), border-color var(--ease), transform var(--ease), opacity var(--ease);
}

.btn:hover:not(:disabled) {
  background: var(--surface-2);
  border-color: rgba(245, 158, 11, 0.45);
}

.btn:active:not(:disabled) {
  transform: translateY(1px);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn:focus-visible,
.board:focus-visible,
.footer a:focus-visible,
.segmented input:focus-visible + span,
.promo:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
}

.btn-accent {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-ink);
}

.btn-accent:hover:not(:disabled) {
  background: #fbbf24;
  border-color: #fbbf24;
}

.btn-ghost {
  background: transparent;
  box-shadow: none;
}

.lang {
  min-width: 44px;
  padding: 0 10px;
  letter-spacing: 0.06em;
}

/* Layout */
.layout {
  flex: 1;
  width: 100%;
  max-width: 920px;
  margin: 0 auto;
  padding: 4px 16px 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

.board-wrap {
  width: var(--board-size);
  flex: none;
}

.panel {
  width: var(--board-size);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

/* Board */
.board {
  width: var(--board-size);
  height: var(--board-size);
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow), 0 0 0 1px rgba(148, 163, 184, 0.18);
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;
}

.board-row {
  display: contents;
}

.sq {
  position: relative;
  display: grid;
  place-items: center;
  transition: background-color var(--ease);
}

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

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

.sq::before,
.sq::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  transition: background var(--ease), box-shadow var(--ease);
}

.sq.last::before {
  background: rgba(245, 158, 11, 0.42);
}

.sq.selected::before {
  background: rgba(245, 158, 11, 0.68);
}

.sq.check::before {
  background: radial-gradient(circle, rgba(239, 68, 68, 0.95) 0%, rgba(239, 68, 68, 0.55) 45%, rgba(239, 68, 68, 0) 75%);
}

.sq.target::after {
  inset: 36%;
  border-radius: 50%;
  background: rgba(15, 23, 42, 0.32);
}

.sq.capture-target::after {
  inset: 4%;
  border-radius: 50%;
  box-shadow: inset 0 0 0 calc(var(--sq) * 0.08) rgba(15, 23, 42, 0.32);
}

.board.kbd:focus .sq.cursor {
  box-shadow: inset 0 0 0 3px var(--accent), inset 0 0 0 5px rgba(15, 23, 42, 0.55);
}

.sq.movable {
  cursor: grab;
}

.board.locked .sq {
  cursor: default;
}

.coord {
  position: absolute;
  font-size: max(9px, calc(var(--sq) * 0.19));
  font-weight: 700;
  line-height: 1;
  pointer-events: none;
  z-index: 1;
}

.coord-rank {
  top: 6%;
  left: 7%;
}

.coord-file {
  right: 7%;
  bottom: 6%;
}

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

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

/* Pieces: filled Unicode glyphs coloured with CSS */
.piece {
  position: relative;
  z-index: 1;
  font-family: var(--piece-font);
  font-size: calc(var(--sq) * 0.78);
  line-height: 1;
  pointer-events: none;
}

.piece.w {
  color: #f8fafc;
  -webkit-text-stroke: calc(var(--sq) * 0.03) #1e293b;
  paint-order: stroke fill;
  text-shadow: 0 calc(var(--sq) * 0.03) calc(var(--sq) * 0.04) rgba(2, 6, 23, 0.45);
}

.piece.b {
  color: #111827;
  -webkit-text-stroke: calc(var(--sq) * 0.012) rgba(226, 232, 240, 0.35);
  paint-order: stroke fill;
  text-shadow: 0 calc(var(--sq) * 0.03) calc(var(--sq) * 0.04) rgba(2, 6, 23, 0.35);
}

.piece.sliding {
  z-index: 3;
}

.sq.drag-origin .piece {
  opacity: 0.3;
}

.piece.ghost {
  position: fixed;
  left: 0;
  top: 0;
  z-index: 50;
  width: var(--sq);
  height: var(--sq);
  display: grid;
  place-items: center;
  font-size: calc(var(--sq) * 0.86);
  filter: drop-shadow(0 8px 10px rgba(2, 6, 23, 0.5));
}

/* Side panel */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 14px 16px;
}

.status-card {
  transition: border-color var(--ease);
}

.status-card.over {
  border-color: var(--accent);
}

.status-card.in-check {
  border-color: rgba(239, 68, 68, 0.7);
}

.status-line {
  margin: 0 0 10px;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.05rem;
}

.turn-swatch {
  width: 14px;
  height: 14px;
  flex: none;
  border-radius: 50%;
  background: #f8fafc;
  box-shadow: 0 0 0 2px var(--surface-2), 0 0 0 3px var(--muted);
  transition: background var(--ease);
}

.status-card[data-turn="b"] .turn-swatch {
  background: #111827;
}

.players {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 4px;
}

.player {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 36px;
  padding: 2px 10px;
  border-radius: 10px;
  color: var(--muted);
  border: 1px solid transparent;
  transition: background var(--ease), color var(--ease), border-color var(--ease);
}

.player.active {
  background: rgba(245, 158, 11, 0.1);
  border-color: rgba(245, 158, 11, 0.35);
  color: var(--text);
}

.player .piece {
  --sq: 34px;
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  border-radius: 8px;
  background: var(--dark-sq);
  font-size: 22px;
}

.player-name {
  flex: 1;
  font-weight: 600;
}

.thinking {
  display: inline-flex;
  gap: 4px;
}

.thinking[hidden] {
  display: none;
}

.thinking i {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--accent);
  animation: pulse 900ms ease-in-out infinite;
}

.thinking i:nth-child(2) {
  animation-delay: 150ms;
}

.thinking i:nth-child(3) {
  animation-delay: 300ms;
}

@keyframes pulse {
  0%, 100% { opacity: 0.25; transform: translateY(0); }
  50% { opacity: 1; transform: translateY(-3px); }
}

.moves-card {
  display: flex;
  flex-direction: column;
  min-height: 0;
}

.moves-card h2 {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin-bottom: 8px;
}

#moves-empty {
  margin: 0;
  font-size: 0.92rem;
}

.move-list {
  list-style: none;
  margin: 0;
  padding: 0;
  max-height: 168px;
  overflow-y: auto;
  font-variant-numeric: tabular-nums;
  scrollbar-width: thin;
  scrollbar-color: var(--surface-2) transparent;
}

.move-list li {
  display: grid;
  grid-template-columns: 2.6em 1fr 1fr;
  align-items: center;
  border-radius: 8px;
}

.move-list li:nth-child(odd) {
  background: rgba(148, 163, 184, 0.05);
}

.move-no {
  color: var(--muted);
  padding-left: 6px;
}

.san {
  padding: 3px 8px;
  border-radius: 6px;
  font-weight: 600;
}

.san.current {
  background: rgba(245, 158, 11, 0.22);
  color: #fcd34d;
}

.move-list li.result {
  display: block;
  padding: 4px 8px;
  text-align: center;
  font-weight: 700;
  color: var(--accent);
}

.actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.actions .btn {
  padding: 0 8px;
}

.hint {
  margin: 0;
  font-size: 0.82rem;
}

/* Footer */
.footer {
  padding: 12px 16px 20px;
  text-align: center;
  font-size: 0.88rem;
  color: var(--muted);
}

.footer a {
  display: inline-flex;
  align-items: center;
  min-height: 40px;
  padding: 0 6px;
  color: var(--accent);
  text-decoration: none;
  border-radius: 4px;
}

.footer a:hover {
  text-decoration: underline;
}

/* Dialogs */
.dialog {
  width: min(92vw, 380px);
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  box-shadow: 0 24px 60px rgba(2, 6, 23, 0.6);
}

.dialog::backdrop {
  background: rgba(2, 6, 23, 0.6);
  backdrop-filter: blur(3px);
}

.dialog[open] {
  animation: pop 200ms ease-out;
}

@keyframes pop {
  from { opacity: 0; transform: translateY(8px) scale(0.98); }
  to { opacity: 1; transform: none; }
}

.dialog h2 {
  font-size: 1.15rem;
  margin-bottom: 14px;
}

.field {
  margin: 0 0 14px;
  padding: 0;
  border: 0;
  transition: opacity var(--ease);
}

.field:disabled {
  opacity: 0.4;
}

.field legend {
  padding: 0;
  margin-bottom: 6px;
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.segmented {
  display: flex;
  gap: 4px;
  padding: 4px;
  border-radius: var(--radius);
  background: var(--bg);
  border: 1px solid var(--border);
}

.segmented label {
  flex: 1;
  position: relative;
}

.segmented input {
  position: absolute;
  opacity: 0;
  inset: 0;
  margin: 0;
}

.segmented span {
  display: grid;
  place-items: center;
  min-height: 40px;
  padding: 0 8px;
  border-radius: 9px;
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  color: var(--muted);
  transition: background var(--ease), color var(--ease);
}

.segmented input:checked + span {
  background: var(--accent);
  color: var(--accent-ink);
}

.field:disabled .segmented span {
  cursor: not-allowed;
}

.dialog-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
  margin-top: 6px;
}

.promo-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-bottom: 12px;
}

.promo {
  --sq: 64px;
  aspect-ratio: 1;
  min-height: 56px;
  display: grid;
  place-items: center;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--dark-sq);
  cursor: pointer;
  transition: background var(--ease), transform var(--ease);
}

.promo:hover {
  background: var(--accent);
  transform: translateY(-2px);
}

.promo .piece {
  font-size: 44px;
}

/* Toast */
.toast {
  position: fixed;
  left: 50%;
  bottom: 24px;
  z-index: 60;
  max-width: calc(100vw - 32px);
  padding: 10px 16px;
  border-radius: var(--radius);
  background: var(--surface-2);
  border: 1px solid rgba(245, 158, 11, 0.45);
  box-shadow: var(--shadow);
  font-weight: 600;
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 12px);
  transition: opacity 200ms ease, transform 200ms ease;
}

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

@media (min-width: 900px) {
  .layout {
    flex-direction: row;
    align-items: flex-start;
    justify-content: center;
    gap: 24px;
    padding-top: 12px;
  }

  .panel {
    width: 300px;
    height: var(--board-size);
  }

  .moves-card {
    flex: 1;
    min-height: 0;
  }

  .move-list {
    max-height: none;
    flex: 1;
  }
}

@media (max-width: 420px) {
  .brand h1 {
    font-size: 1.15rem;
  }

  .btn {
    padding: 0 12px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 1ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 1ms !important;
  }
}