/* Reset and base styles */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    /* Tiles */
    --color-white-tile: #FFFFFF;
    --color-black-tile: #1a1a1a;
    --color-tapped-tile: #4a4a4a;
    --color-grid-line: #cccccc;

    /* Feedback */
    --color-error-flash: #e74c3c;
    --color-miss-flash: #f39c12;

    /* UI */
    --color-background: #2c3e50;
    --color-primary: #3498db;
    --color-primary-hover: #2980b9;
    --color-text: #FFFFFF;
    --color-text-dark: #1a1a1a;

    /* HUD */
    --color-hud-bg: rgba(0, 0, 0, 0.7);

    /* States */
    --color-overlay: rgba(0, 0, 0, 0.85);

    /* Transitions */
    --transition-speed: 0.3s;
}

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background-color: var(--color-background);
    color: var(--color-text);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Prevent selection */
body {
    -webkit-user-select: none;
    -moz-user-select: none;
    user-select: none;
    -webkit-touch-callout: none;
}

/* Screen system */
.screen {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    height: 100dvh;
}

.screen.active {
    display: flex;
    justify-content: center;
    align-items: center;
}

/* Menu Screen */
#menu-screen {
    background: linear-gradient(135deg, var(--color-background) 0%, #1a252f 100%);
}

.menu-content {
    text-align: center;
    padding: 20px;
    max-width: 320px;
    width: 100%;
}

.title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    line-height: 1.2;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.subtitle {
    font-size: 1.1rem;
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 30px;
}

/* Buttons */
.btn {
    display: block;
    width: 100%;
    padding: 16px 24px;
    font-size: 1.2rem;
    font-weight: 600;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
    transition: transform var(--transition-speed), background-color var(--transition-speed);
    min-height: 56px;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-text);
}

.btn-primary:hover {
    background-color: var(--color-primary-hover);
}

.btn-secondary {
    background-color: #27ae60;
    color: var(--color-text);
}

.btn-secondary:hover {
    background-color: #219a52;
}

.btn-tertiary {
    background-color: rgba(255, 255, 255, 0.2);
    color: var(--color-text);
}

.btn-tertiary:hover {
    background-color: rgba(255, 255, 255, 0.3);
}

/* High score display */
.high-score-display {
    margin-top: 30px;
    font-size: 1.3rem;
    color: #f1c40f;
}

/* Instructions */
.instructions {
    margin-top: 40px;
    display: flex;
    justify-content: center;
    gap: 30px;
}

.instruction-item {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 1rem;
}

.tile-black,
.tile-white {
    width: 30px;
    height: 40px;
    border-radius: 4px;
    border: 2px solid var(--color-grid-line);
}

.tile-black {
    background-color: var(--color-black-tile);
}

.tile-white {
    background-color: var(--color-white-tile);
}

/* Game Screen */
#game-screen {
    background-color: var(--color-white-tile);
}

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

/* Game Over Screen */
#gameover-screen {
    background-color: var(--color-overlay);
    z-index: 100;
}

.gameover-content {
    text-align: center;
    padding: 30px;
    max-width: 320px;
    width: 100%;
}

.gameover-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 15px;
    color: var(--color-error-flash);
}

.gameover-reason {
    font-size: 1rem;
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 20px;
}

.gameover-score {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 10px;
}

.new-record {
    font-size: 1.3rem;
    color: #f1c40f;
    margin-bottom: 10px;
    animation: pulse 0.5s ease-in-out infinite alternate;
}

.new-record.hidden {
    display: none;
}

@keyframes pulse {
    from {
        transform: scale(1);
    }
    to {
        transform: scale(1.1);
    }
}

.gameover-best {
    font-size: 1.2rem;
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 30px;
}

.gameover-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

/* Hide utility */
.hidden {
    display: none !important;
}

/* Media queries for larger screens */
@media (min-width: 768px) {
    .title {
        font-size: 3rem;
    }

    .menu-content,
    .gameover-content {
        max-width: 400px;
    }

    .btn {
        font-size: 1.3rem;
    }
}