:root {
  --bg-primary: #0D1117;
  --bg-secondary: #161B22;
  --bg-tertiary: #21262D;
  --text-primary: #F0F6FC;
  --text-secondary: #8B949E;
  --text-muted: #484F58;
  --accent: #3B82F6;
  --border: #30363D;
  --btn-bg: #21262D;
  --btn-active: #30363D;
  --overlay-bg: rgba(0,0,0,0.85);
  --board-bg: #0A0E14;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg-primary: #FFFFFF;
    --bg-secondary: #F6F8FA;
    --bg-tertiary: #E9ECF0;
    --text-primary: #1B1E28;
    --text-secondary: #57606A;
    --text-muted: #8C959F;
    --accent: #3182F6;
    --border: #D0D7DE;
    --btn-bg: #E9ECF0;
    --btn-active: #D0D7DE;
    --overlay-bg: rgba(255,255,255,0.9);
    --board-bg: #F0F2F5;
  }
}

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

html, body {
  height: 100%;
  width: 100%;
  overflow: hidden;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Pretendard', 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100dvh;
}

#app {
  width: 100%;
  max-width: 480px;
  height: 100dvh;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

/* ── Overlay Screens ── */
.screen {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background: var(--overlay-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 100;
  padding: 2rem;
  gap: 1.5rem;
  transition: opacity 0.3s ease;
}

.screen.hidden {
  opacity: 0;
  pointer-events: none;
}

/* ── Title ── */
.game-title {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: 0.15em;
  background: linear-gradient(135deg, var(--accent) 0%, #a78bfa 50%, #f472b6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  text-align: center;
  line-height: 1.1;
}

.game-subtitle {
  font-size: 0.85rem;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

/* ── Stats Card ── */
.stats-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.5rem;
  display: flex;
  gap: 2rem;
  align-items: center;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
}

.stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-value.wins { color: #22c55e; }
.stat-value.losses { color: #ef4444; }
.stat-value.draws { color: #f59e0b; }

.stat-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ── Buttons ── */
.btn {
  border: none;
  border-radius: 10px;
  font-family: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  letter-spacing: 0.02em;
}

.btn:active {
  transform: scale(0.96);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  font-size: 1rem;
  padding: 0.875rem 2.5rem;
  width: 100%;
  max-width: 260px;
  box-shadow: 0 4px 16px rgba(59,130,246,0.3);
}

.btn-primary:hover {
  filter: brightness(1.1);
  box-shadow: 0 6px 20px rgba(59,130,246,0.4);
}

.btn-secondary {
  background: var(--btn-bg);
  color: var(--text-secondary);
  font-size: 0.85rem;
  padding: 0.625rem 1.5rem;
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--btn-active);
  color: var(--text-primary);
}

.btn-icon {
  background: var(--btn-bg);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  padding: 0.5rem;
  border-radius: 8px;
  font-size: 1rem;
  width: 36px;
  height: 36px;
}

.btn-icon:hover {
  background: var(--btn-active);
  color: var(--text-primary);
}

/* ── Result Screen ── */
.result-emoji {
  font-size: 4rem;
  animation: bounceIn 0.5s ease;
}

.result-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text-primary);
}

.result-subtitle {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

@keyframes bounceIn {
  0% { transform: scale(0.3); opacity: 0; }
  60% { transform: scale(1.15); opacity: 1; }
  100% { transform: scale(1); }
}

/* ── Game Header ── */
#game-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1rem;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.header-title {
  font-size: 1rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), #a78bfa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.header-controls {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

/* ── Player Info ── */
.player-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.6rem 1rem;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  gap: 0.75rem;
}

.player-bar.top {
  border-bottom: 1px solid var(--border);
  border-top: none;
}

.player-bar.bottom {
  border-top: 1px solid var(--border);
  border-bottom: none;
}

.player-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  min-width: 0;
}

.player-indicator {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
  transition: all 0.3s ease;
}

.player-indicator.white { background: #e5e7eb; border: 2px solid #9ca3af; }
.player-indicator.black { background: #1f2937; border: 2px solid #6b7280; }
.player-indicator.active {
  box-shadow: 0 0 0 3px var(--accent), 0 0 8px var(--accent);
  animation: pulse 1.5s infinite;
}

@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 3px var(--accent), 0 0 8px var(--accent); }
  50% { box-shadow: 0 0 0 5px var(--accent), 0 0 16px var(--accent); }
}

.player-name {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.player-status {
  font-size: 0.7rem;
  color: var(--text-muted);
  white-space: nowrap;
}

.player-status.in-check {
  color: #ef4444;
  font-weight: 600;
  animation: checkFlash 0.8s infinite alternate;
}

@keyframes checkFlash {
  from { opacity: 1; }
  to { opacity: 0.4; }
}

/* ── Captured Pieces ── */
.captured-pieces {
  font-size: 0.7rem;
  display: flex;
  flex-wrap: wrap;
  gap: 1px;
  max-width: 200px;
  align-items: center;
}

.captured-pieces span {
  font-size: 0.85rem;
  line-height: 1;
  opacity: 0.7;
}

/* ── Board Container ── */
#board-container {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 0.5rem;
  background: var(--board-bg);
  position: relative;
  min-height: 0;
}

#board-wrap {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ── Chess Board ── */
#chess-board {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  border: 2px solid var(--border);
  border-radius: 4px;
  overflow: hidden;
  box-shadow: 0 8px 32px rgba(0,0,0,0.4);
  /* Size calculated dynamically in JS */
}

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  cursor: pointer;
  transition: background-color 0.15s ease;
  user-select: none;
  -webkit-user-select: none;
}

.cell.light {
  background: #f0d9b5;
}

.cell.dark {
  background: #b58863;
}

@media (prefers-color-scheme: light) {
  .cell.light { background: #f0d9b5; }
  .cell.dark { background: #b58863; }
}

.cell.selected {
  background: rgba(106, 168, 79, 0.8) !important;
}

.cell.valid-move::after {
  content: '';
  position: absolute;
  width: 30%;
  height: 30%;
  border-radius: 50%;
  background: rgba(0, 0, 0, 0.25);
  pointer-events: none;
}

.cell.valid-capture::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 0;
  border: 4px solid rgba(0, 0, 0, 0.25);
  background: transparent;
  pointer-events: none;
}

.cell.last-move {
  background: rgba(205, 210, 106, 0.6) !important;
}

.cell.in-check {
  background: rgba(239, 68, 68, 0.6) !important;
}

.cell.hover:not(.selected) {
  filter: brightness(1.1);
}

/* ── Chess Piece ── */
.piece {
  font-size: 1em;
  line-height: 1;
  z-index: 1;
  transition: transform 0.1s ease;
  pointer-events: none;
  text-shadow: 0 1px 3px rgba(0,0,0,0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 85%;
  height: 85%;
}

.cell:active .piece {
  transform: scale(1.1);
}

/* ── Rank/File Labels ── */
.rank-labels, .file-labels {
  position: absolute;
  display: flex;
  pointer-events: none;
  z-index: 5;
}

.rank-labels {
  flex-direction: column;
  left: -1.2rem;
  top: 0;
  height: 100%;
}

.file-labels {
  flex-direction: row;
  bottom: -1.2rem;
  left: 0;
  width: 100%;
}

.rank-labels span,
.file-labels span {
  font-size: 0.6rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
}

.rank-labels span { flex: 1; }
.file-labels span { flex: 1; }

/* ── Bottom Panel ── */
#bottom-panel {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  flex-shrink: 0;
}

.panel-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}

.tab-btn {
  flex: 1;
  padding: 0.5rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.15s ease;
  letter-spacing: 0.03em;
}

.tab-btn:hover {
  color: var(--text-secondary);
}

.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.tab-content {
  display: none;
  height: 80px;
  overflow-y: auto;
  padding: 0.5rem;
}

.tab-content.active {
  display: block;
}

/* ── Move History ── */
#move-list {
  display: grid;
  grid-template-columns: auto 1fr 1fr;
  gap: 0.1rem 0.5rem;
  font-size: 0.72rem;
  color: var(--text-secondary);
  font-family: 'SF Mono', 'Fira Code', monospace;
}

.move-num {
  color: var(--text-muted);
  text-align: right;
  padding-right: 0.25rem;
}

.move-text {
  cursor: default;
  padding: 0.1rem 0.25rem;
  border-radius: 3px;
}

.move-text:hover {
  background: var(--bg-tertiary);
}

.move-text.last {
  color: var(--accent);
  font-weight: 600;
}

/* ── AI Thinking ── */
#ai-thinking {
  display: none;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 0.75rem;
  font-size: 0.75rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
}

#ai-thinking.visible {
  display: flex;
}

.thinking-dots {
  display: flex;
  gap: 3px;
}

.thinking-dots span {
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--accent);
  animation: dotBounce 1.2s ease-in-out infinite;
}

.thinking-dots span:nth-child(2) { animation-delay: 0.2s; }
.thinking-dots span:nth-child(3) { animation-delay: 0.4s; }

@keyframes dotBounce {
  0%, 80%, 100% { transform: translateY(0); opacity: 0.4; }
  40% { transform: translateY(-4px); opacity: 1; }
}

/* ── Status Bar ── */
#status-bar {
  padding: 0.4rem 1rem;
  font-size: 0.75rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border);
}

.status-text {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

/* ── Promotion Modal ── */
#promotion-modal {
  display: none;
  position: absolute;
  inset: 0;
  background: var(--overlay-bg);
  backdrop-filter: blur(8px);
  z-index: 200;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1rem;
}

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

.promo-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.promo-pieces {
  display: flex;
  gap: 0.75rem;
}

.promo-piece {
  width: 60px;
  height: 60px;
  background: var(--bg-secondary);
  border: 2px solid var(--border);
  border-radius: 12px;
  font-size: 2.2rem;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s ease;
}

.promo-piece:hover {
  border-color: var(--accent);
  background: var(--bg-tertiary);
  transform: scale(1.05);
}

/* ── Scrollbar ── */
::-webkit-scrollbar {
  width: 4px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 2px;
}

/* ── Difficulty selector ── */
.difficulty-row {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.diff-btn {
  padding: 0.4rem 0.9rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--btn-bg);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.15s ease;
}

.diff-btn:hover {
  background: var(--btn-active);
  color: var(--text-primary);
}

.diff-btn.selected {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}