:root {
  --board-size: min(78vh, 560px);
  --square-size: calc(var(--board-size) / 8);
  --light-square: #ecd8b8;
  --dark-square: #ae7a4e;
  --light-selected: #f7ec5d;
  --dark-selected: #d4b625;
  --light-move: rgba(100, 180, 70, 0.45);
  --dark-move: rgba(80, 150, 50, 0.5);
  --light-last: rgba(160, 140, 60, 0.35);
  --dark-last: rgba(140, 120, 40, 0.35);
  --check-color: rgba(235, 50, 50, 0.5);
  --coord-size: 20px;
  --border-color: #5c3a1e;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
}

.game-container {
  background: linear-gradient(145deg, #2a2a3e, #1e1e30);
  padding: 28px;
  border-radius: 20px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5), inset 0 1px 0 rgba(255, 255, 255, 0.05);
}

/* 游戏信息 */
.game-info {
  text-align: center;
  margin-bottom: 16px;
}

.player-turn {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 10px;
  color: #e8e8f0;
  letter-spacing: 0.02em;
}

.captured-pieces {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.captured {
  flex: 1;
  min-height: 40px;
  padding: 6px 10px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
  font-size: 1.3rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px;
}

/* 棋盘外框 */
.board-wrapper {
  background: var(--border-color);
  border-radius: 8px;
  padding: 4px;
  box-shadow:
    0 8px 24px rgba(0, 0, 0, 0.4),
    inset 0 2px 4px rgba(255, 255, 255, 0.1);
  position: relative;
}

/* 坐标标注 */
.board-with-coords {
  display: grid;
  grid-template-columns: var(--coord-size) var(--board-size) var(--coord-size);
  grid-template-rows: var(--coord-size) var(--board-size) var(--coord-size);
  align-items: center;
  justify-items: center;
}

.coord-row {
  display: flex;
  width: var(--board-size);
}

.coord-row span {
  flex: 1;
  text-align: center;
  color: rgba(255, 255, 255, 0.4);
  font-size: 0.75rem;
  font-weight: 600;
  user-select: none;
}

.coord-col {
  display: flex;
  flex-direction: column;
  height: var(--board-size);
}

.coord-col span {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(255, 255, 255, 0.4);
  font-size: 0.75rem;
  font-weight: 600;
  user-select: none;
}

/* 棋盘 */
.chessboard {
  display: grid;
  grid-template-columns: repeat(8, var(--square-size));
  grid-template-rows: repeat(8, var(--square-size));
  width: var(--board-size);
  height: var(--board-size);
  border-radius: 4px;
  overflow: hidden;
}

/* 格子 */
.square {
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  position: relative;
  transition: none;
  /* 棋子文字样式 */
  font-size: calc(var(--square-size) * 0.78);
  line-height: 1;
  user-select: none;
  -webkit-user-select: none;
}

.square.light {
  background-color: var(--light-square);
}

.square.dark {
  background-color: var(--dark-square);
}

/* 选中的格子 */
.square.light.selected {
  background-color: var(--light-selected);
}

.square.dark.selected {
  background-color: var(--dark-selected);
}

/* 上一步移动 */
.square.light.last-move {
  background-color: #d8d27c;
}

.square.dark.last-move {
  background-color: #a8a040;
}

/* 可走位置：空格用圆点，有子用圆环 */
.square.possible-move::after {
  content: "";
  position: absolute;
  border-radius: 50%;
  pointer-events: none;
}

.square.possible-move:not([data-piece])::after {
  width: 28%;
  height: 28%;
  background: rgba(0, 0, 0, 0.18);
}

.square.possible-move[data-piece]::after {
  width: 88%;
  height: 88%;
  border: 5px solid rgba(0, 0, 0, 0.18);
  background: transparent;
}

/* 将军高亮 */
.square.in-check {
  background: radial-gradient(ellipse at center, #ff3030 0%, #cc0000 40%, transparent 70%);
}

/* 棋子样式 */
.piece-white,
.piece-black {
  display: inline-block;
  line-height: 1;
}

/* 白子：轮廓字符，白色描边+深色勾勒 */
.piece-white {
  color: #fff;
  text-shadow:
    0 0 2px rgba(0, 0, 0, 0.8),
    0 1px 3px rgba(0, 0, 0, 0.5);
  filter: drop-shadow(0 1px 1px rgba(0, 0, 0, 0.4));
}

/* 黑兵♟字形偏大，单独缩小 */
.piece-black-pawn {
  font-size: 0.82em;
}

/* 黑子：实心字符，本身就是黑色填充 */
.piece-black {
  color: #1a1a1a;
  text-shadow:
    0 0 1px rgba(255, 255, 255, 0.5),
    0 1px 3px rgba(0, 0, 0, 0.4);
  filter: drop-shadow(0 1px 1px rgba(0, 0, 0, 0.3));
}

/* 悬停效果 */
.square:hover {
  filter: brightness(1.08);
}

.square[data-piece]:hover {
  cursor: grab;
}

/* 控制按钮 */
.controls {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-top: 16px;
}

button {
  padding: 10px 24px;
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: 10px;
  background: linear-gradient(135deg, #4a4a6a, #3a3a55);
  color: #e0e0f0;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

button:hover {
  background: linear-gradient(135deg, #5a5a8a, #4a4a70);
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.4);
}

button:active {
  transform: translateY(0);
}

/* 兵升变对话框 */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(4px);
  z-index: 1000;
  justify-content: center;
  align-items: center;
}

.modal.show {
  display: flex;
}

.modal-content {
  background: linear-gradient(145deg, #2a2a3e, #1e1e30);
  padding: 28px 32px;
  border-radius: 16px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.6);
  text-align: center;
}

.modal-content h2 {
  margin-bottom: 16px;
  color: #e8e8f0;
  font-size: 1.2rem;
}

.promotion-choices {
  display: flex;
  gap: 12px;
  justify-content: center;
}

.promotion-piece {
  width: 64px;
  height: 64px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 2.6rem;
  background: var(--light-square);
  border: 3px solid var(--dark-square);
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.2s ease;
  color: #ffffff;
  text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
  filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.3));
}

.promotion-piece:hover {
  transform: translateY(-4px) scale(1.05);
  background: var(--light-selected);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
}

/* 响应式 */
@media (max-width: 768px) {
  :root {
    --board-size: min(88vw, 78vh);
    --coord-size: 16px;
  }

  .game-container {
    padding: 14px;
    border-radius: 14px;
  }

  .player-turn {
    font-size: 1.1rem;
  }

  button {
    padding: 8px 18px;
    font-size: 0.9rem;
  }
}