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

:root {
    --color-bg: #1a1410;
    --color-surface: #2a2118;
    --color-surface-light: #3a2f24;
    --color-text: #f5f0e8;
    --color-text-muted: #b8a898;
    --color-accent: #c8a45c;
    --color-accent-dim: #8a7040;
    --color-black-stone: #1a1a1a;
    --color-white-stone: #f5f0e8;
    --color-border: #4a3f34;
    --color-success: #7cb87c;
    --color-danger: #c87070;
    --font-serif: 'Noto Serif JP', 'Noto Serif SC', 'Source Han Serif SC', 'SimSun', serif;
    --font-sans: 'Noto Sans JP', 'Noto Sans SC', 'Source Han Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    --transition-fast: 180ms ease;
    --transition-med: 250ms ease;
}

html {
    font-size: 16px;
}

body {
    font-family: var(--font-sans);
    background: var(--color-bg);
    color: var(--color-text);
    min-height: 100vh;
    overflow-x: hidden;
    line-height: 1.5;
}

#app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

#game-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 1rem;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    flex-wrap: wrap;
    gap: 0.5rem;
}

#game-header h1 {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-accent);
    letter-spacing: 0.1em;
}

#mode-selector {
    display: flex;
    gap: 0.25rem;
    background: var(--color-bg);
    border-radius: 6px;
    padding: 3px;
}

.mode-btn {
    font-family: var(--font-sans);
    font-size: 0.875rem;
    padding: 0.5rem 1rem;
    min-height: 44px;
    min-width: 44px;
    border: none;
    border-radius: 4px;
    background: transparent;
    color: var(--color-text-muted);
    cursor: pointer;
    transition: background var(--transition-fast), color var(--transition-fast);
}

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

.mode-btn:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

.mode-btn.active {
    background: var(--color-accent-dim);
    color: var(--color-text);
}

#game-main {
    display: flex;
    flex: 1;
    overflow: hidden;
}

#canvas-container {
    flex: 1;
    position: relative;
    min-height: 300px;
}

#game-canvas {
    display: block;
    width: 100%;
    height: 100%;
    touch-action: none;
}

#webgl-error {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--color-surface);
    padding: 2rem;
    text-align: center;
    gap: 0.5rem;
}

#webgl-error p {
    font-size: 1rem;
    color: var(--color-text-muted);
}

#sidebar {
    width: 220px;
    background: var(--color-surface);
    border-left: 1px solid var(--color-border);
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    overflow-y: auto;
}

#status-panel {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

#turn-indicator {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9375rem;
}

#turn-label {
    color: var(--color-text-muted);
}

#turn-value {
    font-weight: 600;
    color: var(--color-text);
}

#move-count {
    display: flex;
    justify-content: space-between;
    font-size: 0.875rem;
    color: var(--color-text-muted);
}

#move-count-value {
    font-weight: 600;
    color: var(--color-text);
}

#game-result {
    padding: 0.5rem;
    border-radius: 4px;
    font-weight: 600;
    text-align: center;
    font-size: 0.9375rem;
}

#game-result.win {
    background: rgba(200, 164, 92, 0.15);
    color: var(--color-accent);
}

#game-result.draw {
    background: rgba(184, 168, 152, 0.15);
    color: var(--color-text-muted);
}

#controls-panel {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

#controls-panel button {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    width: 100%;
    min-height: 44px;
    padding: 0.625rem 1rem;
    font-family: var(--font-sans);
    font-size: 0.9375rem;
    border: 1px solid var(--color-border);
    border-radius: 6px;
    background: var(--color-surface-light);
    color: var(--color-text);
    cursor: pointer;
    transition: background var(--transition-fast), border-color var(--transition-fast);
}

#controls-panel button:hover {
    background: var(--color-border);
    border-color: var(--color-accent-dim);
}

#controls-panel button:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

#controls-panel button:active {
    background: var(--color-accent-dim);
}

#help-panel {
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

#help-panel h2 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 0.5rem;
}

#help-panel ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

#help-panel li {
    padding-left: 0.75rem;
    position: relative;
}

#help-panel li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.5em;
    width: 4px;
    height: 4px;
    border-radius: 50%;
    background: var(--color-accent-dim);
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.hidden {
    display: none !important;
}

@media (max-width: 768px) {
    #game-main {
        flex-direction: column;
    }

    #canvas-container {
        min-height: 50vh;
    }

    #sidebar {
        width: 100%;
        border-left: none;
        border-top: 1px solid var(--color-border);
        flex-direction: row;
        flex-wrap: wrap;
        align-items: flex-start;
        padding: 0.75rem;
        gap: 0.75rem;
    }

    #status-panel {
        flex-direction: row;
        align-items: center;
        gap: 1rem;
        flex: 1;
    }

    #controls-panel {
        flex-direction: row;
    }

    #controls-panel button {
        width: auto;
        flex: 1;
    }

    #help-panel {
        display: none;
    }
}

@media (max-width: 375px) {
    #game-header h1 {
        font-size: 1.1rem;
    }

    .mode-btn {
        font-size: 0.8125rem;
        padding: 0.5rem 0.75rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
    }
}