:root {
  --bg: #1f2329;
  --panel: #2a2f37;
  --panel-border: #3a414c;
  --text: #e8e6e1;
  --text-dim: #9aa1ab;
  --accent: #d4a24e;
  --accent-hover: #e0b161;
  --btn: #3a414c;
  --btn-hover: #464e5a;
  --win: #7cc47f;
  --lose: #d98080;
  --draw: #a0a7b1;
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: "Microsoft JhengHei", "PingFang TC", "Noto Sans TC", sans-serif;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.app {
  display: flex;
  gap: 28px;
  align-items: flex-start;
  flex-wrap: wrap;
  justify-content: center;
}

/* ---------- 側邊面板 ---------- */
.panel {
  width: 300px;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 16px;
  padding: 24px;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
}

.title {
  font-size: 30px;
  font-weight: 700;
  letter-spacing: 6px;
  color: var(--accent);
}

.subtitle {
  font-size: 14px;
  color: var(--text-dim);
  margin: 4px 0 20px;
  letter-spacing: 2px;
}

.model-credit {
  color: var(--text-dim);
  font-size: 11px;
  line-height: 1.5;
  margin: -10px 0 20px;
}

.model-credit strong {
  color: var(--accent);
  font-weight: 600;
}

.group {
  margin-bottom: 20px;
}

.group h2 {
  font-size: 13px;
  color: var(--text-dim);
  font-weight: 600;
  margin-bottom: 8px;
  letter-spacing: 1px;
}

/* 分段按鈕 */
.seg {
  display: flex;
  background: #23272e;
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 4px;
  gap: 4px;
}

.seg button {
  flex: 1;
  background: transparent;
  color: var(--text-dim);
  border: none;
  border-radius: 7px;
  padding: 8px 4px;
  font-size: 14px;
  font-family: inherit;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: background 0.15s, color 0.15s;
}

.seg button:hover {
  color: var(--text);
}

.seg button.active {
  background: var(--accent);
  color: #20242a;
  font-weight: 600;
}

.stone-chip {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  display: inline-block;
}

.stone-chip.black {
  background: radial-gradient(circle at 35% 30%, #555, #000 70%);
}

.stone-chip.white {
  background: radial-gradient(circle at 35% 30%, #fff, #c8c8c8 75%);
}

/* 比分 */
.score {
  display: flex;
  gap: 8px;
}

.score-item {
  flex: 1;
  background: #23272e;
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 10px 6px;
  text-align: center;
}

.score-label {
  display: block;
  font-size: 12px;
  color: var(--text-dim);
  margin-bottom: 4px;
}

.score-value {
  display: block;
  font-size: 22px;
  font-weight: 700;
  color: var(--accent);
}

/* 動作按鈕 */
.actions {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 0;
}

.btn {
  background: var(--btn);
  color: var(--text);
  border: none;
  border-radius: 10px;
  padding: 12px;
  font-size: 15px;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.15s, transform 0.05s;
}

.btn:hover:not(:disabled) {
  background: var(--btn-hover);
}

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

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

.btn.primary {
  background: var(--accent);
  color: #20242a;
  font-weight: 700;
}

.btn.primary:hover:not(:disabled) {
  background: var(--accent-hover);
}

/* ---------- 棋盤區 ---------- */
.board-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.status {
  font-size: 17px;
  min-height: 26px;
  font-weight: 600;
  letter-spacing: 1px;
  color: var(--text);
}

.status.thinking {
  color: var(--accent);
}

.status.win {
  color: var(--win);
}

.status.lose {
  color: var(--lose);
}

.status.draw {
  color: var(--draw);
}

#board {
  background: #b5824a;
  border-radius: 12px;
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.45), inset 0 0 40px rgba(90, 55, 20, 0.35);
  cursor: pointer;
  /* 顯示尺寸一律由 CSS 決定，且固定為正方形（canvas 本身是正方形緩衝區），
     手機上依視窗寬度縮放；避免被拉成長方形導致落子座標錯位 */
  width: min(92vw, 620px);
  aspect-ratio: 1 / 1;
  height: auto;
  touch-action: manipulation; /* 避免雙擊縮放干擾點擊 */
  -webkit-tap-highlight-color: transparent;
}

.hint {
  font-size: 12px;
  color: var(--text-dim);
}

@media (max-width: 1020px) {
  .app {
    flex-direction: column-reverse;
    align-items: center;
  }
  .panel {
    width: min(92vw, 620px);
  }
}