:root {
    --primary: #00CEC9;
    --secondary: #81ECEC;
    --accent: #FF7675;
    --bg: #0A1A1A;
    --text: #FFFFFF;
    --glass: rgba(255, 255, 255, 0.1);
    --font-stack: 'Inter', system-ui, -apple-system, sans-serif;
    --border-radius: 12px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: var(--font-stack);
}

body {
    background-color: var(--bg);
    color: var(--text);
    overflow: hidden;
    width: 100vw;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    user-select: none;
    -webkit-user-select: none;
}

#game-container {
    position: relative;
    width: 100%;
    height: 100%;
}

canvas {
    display: block;
    width: 100%;
    height: 100%;
    background-color: var(--bg);
}

#ui-layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none; /* Let clicks pass through to canvas unless on button */
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.screen {
    position: absolute;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
    background: rgba(10, 26, 26, 0.85);
    backdrop-filter: blur(10px);
    padding: 40px;
    border-radius: var(--border-radius);
    border: 1px solid var(--glass);
    text-align: center;
    pointer-events: all;
    transition: opacity 0.3s ease;
}

.hidden {
    display: none !important;
}

.title {
    font-size: 3rem;
    font-weight: 800;
    letter-spacing: -2px;
    color: var(--primary);
    text-shadow: 0 0 20px rgba(0, 206, 201, 0.5);
}

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

.instruction {
    font-size: 1.2rem;
    color: var(--secondary);
    opacity: 0.8;
}

.btn {
    background: var(--primary);
    color: var(--bg);
    border: none;
    padding: 15px 40px;
    font-size: 1.2rem;
    font-weight: 700;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: transform 0.1s, box-shadow 0.2s;
    text-transform: uppercase;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 206, 201, 0.4);
}

.btn:active {
    transform: translateY(1px);
}

.high-score-display {
    margin-top: 10px;
    font-size: 0.9rem;
    opacity: 0.7;
}

#hud {
    position: absolute;
    top: 20px;
    left: 20px;
    display: flex;
    gap: 20px;
    pointer-events: none;
}

.hud-item {
    background: var(--glass);
    padding: 10px 20px;
    border-radius: var(--border-radius);
    backdrop-filter: blur(5px);
    border: 1px solid rgba(255,255,255,0.05);
}

.hud-item .label {
    display: block;
    font-size: 0.7rem;
    color: var(--secondary);
    margin-bottom: 2px;
    letter-spacing: 1px;
}

#score-display, #multiplier-display {
    font-size: 1.5rem;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
}