:root {
    --bg-color: #0f172a;
    --text-color: #e2e8f0;
    --accent-color: #10b981; /* 綠色蛇身 */
    --food-color: #ef4444;   /* 紅色食物 */
    --panel-bg: rgba(30, 41, 59, 0.7);
    --border-color: rgba(255, 255, 255, 0.1);
    --font-main: 'Orbitron', sans-serif;
    --font-ui: 'Roboto', sans-serif;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    user-select: none;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-ui);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    overflow: hidden;
    /* 加入微妙的背景漸層動態效果 */
    background: radial-gradient(circle at center, #1e293b 0%, #0f172a 100%);
}

.game-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    background: var(--panel-bg);
    padding: 2rem;
    border-radius: 20px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5), 
                inset 0 1px 0 rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
}

header {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

h1 {
    font-family: var(--font-main);
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: 2px;
    background: linear-gradient(135deg, #10b981 0%, #3b82f6 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 0 20px rgba(16, 185, 129, 0.3);
}

.score-board {
    display: flex;
    gap: 1.5rem;
}

.score-box {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
}

.score-box .label {
    font-size: 0.75rem;
    color: #94a3b8;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.score-box .value {
    font-family: var(--font-main);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
}

.canvas-wrapper {
    position: relative;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 0 0 2px var(--border-color),
                0 10px 30px rgba(0, 0, 0, 0.5);
    background-color: #000;
}

canvas {
    display: block;
    /* 讓畫質在高 DPI 螢幕上維持清晰 (由 JS 處理 scale，此處設定基本樣式) */
}

/* 遊戲結束遮罩 Glassmorphism */
.overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(8px);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 10;
    opacity: 1;
    transition: opacity 0.3s ease;
}

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

.overlay h2 {
    font-family: var(--font-main);
    font-size: 3rem;
    color: #ef4444;
    margin-bottom: 0.5rem;
    text-shadow: 0 0 20px rgba(239, 68, 68, 0.5);
    letter-spacing: 3px;
}

.overlay p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    color: #cbd5e1;
}

#finalScore {
    font-family: var(--font-main);
    font-weight: 700;
    color: #10b981;
}

button {
    font-family: var(--font-main);
    font-size: 1.25rem;
    font-weight: 700;
    letter-spacing: 2px;
    padding: 12px 32px;
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    box-shadow: 0 0 15px rgba(16, 185, 129, 0.4);
    transition: all 0.2s ease;
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 25px rgba(16, 185, 129, 0.6);
}

button:active {
    transform: translateY(1px);
}

footer {
    margin-top: 1.5rem;
    color: #64748b;
    font-size: 0.875rem;
}

kbd {
    background-color: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 4px;
    padding: 2px 6px;
    font-family: var(--font-main);
    font-size: 0.75rem;
    color: #e2e8f0;
    display: inline-block;
}