/* ==================== CSS 变量：浅色模式（默认） ==================== */
:root {
    --bg-color: #f5f0e8;
    --container-bg: #ffffff;
    --text-color: #333333;
    --text-secondary: #666666;
    --board-bg: #e8c97b;
    --board-line: #5d4037;
    --star-dot: #5d4037;
    --btn-bg: #f0e6d3;
    --btn-hover: #e0d0b8;
    --btn-text: #333333;
    --btn-border: #c0a880;
    --btn-black-bg: #333333;
    --btn-black-text: #ffffff;
    --btn-white-bg: #fafafa;
    --btn-white-text: #333333;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
    --status-bg: #fdf6e3;
    --status-text: #5d4037;
    --canvas-shadow: 0 6px 30px rgba(0, 0, 0, 0.2);
    --select-panel-bg: #fdf6e3;
    --win-highlight: #ff4444;
    --last-move-dot: #ff6600;
    --params-bg: #f0f0f0;
}

body.dark-mode {
    --bg-color: #1a1a2e;
    --container-bg: #252540;
    --text-color: #e0e0e0;
    --text-secondary: #b0b0b0;
    --board-bg: #6d4c2e;
    --board-line: #c0a080;
    --star-dot: #c0a080;
    --btn-bg: #3a3a55;
    --btn-hover: #4a4a65;
    --btn-text: #e0e0e0;
    --btn-border: #555577;
    --btn-black-bg: #cccccc;
    --btn-black-text: #1a1a2e;
    --btn-white-bg: #e8e8e8;
    --btn-white-text: #1a1a2e;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
    --status-bg: #333350;
    --status-text: #e0c080;
    --canvas-shadow: 0 6px 30px rgba(0, 0, 0, 0.6);
    --select-panel-bg: #333350;
    --win-highlight: #ff6b6b;
    --last-move-dot: #ff9933;
    --params-bg: #2e2e40;
}

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

body {
    background-color: var(--bg-color);
    font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
    color: var(--text-color);
    padding: 20px;
}

.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 2px solid var(--btn-border);
    background-color: var(--btn-bg);
    cursor: pointer;
    font-size: 22px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    z-index: 100;
    box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}
.theme-toggle:hover {
    background-color: var(--btn-hover);
    transform: scale(1.08);
}

.container {
    background-color: var(--container-bg);
    border-radius: 20px;
    padding: 30px 35px 35px;
    box-shadow: var(--shadow);
    text-align: center;
    transition: all 0.3s ease;
    max-width: 750px;
    width: 100%;
}

.title {
    font-size: 2.2rem;
    font-weight: 700;
    margin-bottom: 2px;
    letter-spacing: 4px;
    color: var(--text-color);
}
.subtitle {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
    letter-spacing: 2px;
}

.status-bar {
    background-color: var(--status-bg);
    color: var(--status-text);
    padding: 10px 20px;
    border-radius: 25px;
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 18px;
    display: inline-block;
    min-width: 180px;
    transition: all 0.3s ease;
}

.select-panel {
    background-color: var(--select-panel-bg);
    border-radius: 16px;
    padding: 25px 20px;
    margin-bottom: 10px;
    transition: all 0.3s ease;
}
.select-hint {
    font-size: 1rem;
    color: var(--text-color);
    margin-bottom: 18px;
    font-weight: 500;
}
.select-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
    flex-wrap: wrap;
}

.stone {
    display: inline-block;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    vertical-align: middle;
    margin-right: 6px;
    position: relative;
    top: -1px;
}
.black-stone {
    background: radial-gradient(circle at 35% 30%, #555, #111);
    box-shadow: 1px 2px 4px rgba(0,0,0,0.4);
}
.white-stone {
    background: radial-gradient(circle at 35% 30%, #fff, #ddd);
    border: 2px solid #999;
    box-shadow: 1px 2px 4px rgba(0,0,0,0.2);
}

.btn {
    padding: 12px 28px;
    border-radius: 30px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    border: 2px solid var(--btn-border);
    background-color: var(--btn-bg);
    color: var(--btn-text);
    transition: all 0.25s ease;
    letter-spacing: 1px;
    white-space: nowrap;
}
.btn:hover {
    background-color: var(--btn-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 14px rgba(0,0,0,0.18);
}
.btn:active {
    transform: translateY(0);
    box-shadow: none;
}
.btn-black {
    background-color: var(--btn-black-bg);
    color: var(--btn-black-text);
    border-color: var(--btn-black-bg);
}
.btn-black:hover { opacity: 0.85; }
.btn-white {
    background-color: var(--btn-white-bg);
    color: var(--btn-white-text);
    border-color: #aaa;
}
.btn-white:hover { background-color: #f0f0f0; }
body.dark-mode .btn-white:hover { background-color: #d0d0d0; }
.btn-restart {
    margin-top: 16px;
    font-size: 1.05rem;
    padding: 12px 35px;
    background-color: #ff8c42;
    color: #fff;
    border-color: #ff8c42;
}
.btn-restart:hover { background-color: #ff7730; border-color: #ff7730; }

.board-wrapper {
    display: inline-block;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--canvas-shadow);
    transition: box-shadow 0.3s ease;
}
.board-wrapper canvas {
    display: block;
    max-width: 100%;
    height: auto;
    cursor: pointer;
    border-radius: 12px;
}

/* 参数面板样式 */
.params-panel {
    margin-top: 20px;
    background-color: var(--params-bg);
    border-radius: 12px;
    padding: 15px 20px;
    transition: all 0.3s ease;
}
.params-info {
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--text-color);
}
.params-buttons {
    display: flex;
    gap: 10px;
    justify-content: center;
    flex-wrap: wrap;
}
.btn-small {
    padding: 8px 18px;
    font-size: 0.85rem;
    border-radius: 20px;
}
.params-note {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 8px;
}

@media (max-width: 700px) {
    .container { padding: 20px 12px 22px; border-radius: 14px; }
    .title { font-size: 1.5rem; letter-spacing: 2px; }
    .subtitle { font-size: 0.8rem; margin-bottom: 10px; }
    .status-bar { font-size: 0.85rem; padding: 8px 16px; margin-bottom: 10px; }
    .select-buttons { gap: 10px; }
    .btn { padding: 10px 18px; font-size: 0.85rem; }
    .board-wrapper canvas { max-width: 95vw; }
}