:root {
    --game-bg: #70c5ce;
    --pipe-green: #90ee90;
    --pipe-dark: #228b22;
    --bird-yellow: #ffd700;
    --text-white: #ffffff;
    --shadow-black: rgba(0, 0, 0, 0.3);
    --game-width: 400px;
    --game-height: 600px;
}

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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #87ceeb, #98fb98);
    font-family: 'Arial', sans-serif;
}

.game-container {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

#gameCanvas {
    border: 3px solid #333;
    border-radius: 10px;
    background: var(--game-bg);
    box-shadow: 0 4px 20px var(--shadow-black);
    max-width: 100%;
    height: auto;
}

.game-over, .start-screen {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(0, 0, 0, 0.8);
    color: var(--text-white);
    padding: 30px;
    border-radius: 15px;
    text-align: center;
    box-shadow: 0 4px 20px var(--shadow-black);
    z-index: 10;
}

.game-over.hidden, .start-screen.hidden {
    display: none;
}

.game-over h2, .start-screen h1 {
    margin-bottom: 20px;
    font-size: 2.5em;
}

.game-over p, .start-screen p {
    margin-bottom: 20px;
    font-size: 1.2em;
}

button {
    background: var(--bird-yellow);
    color: #333;
    border: none;
    padding: 12px 24px;
    font-size: 1.1em;
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

button:hover {
    background: #ffed4e;
    transform: scale(1.05);
}

.score-display {
    position: absolute;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    color: var(--text-white);
    font-size: 2em;
    font-weight: bold;
    text-shadow: 2px 2px 4px var(--shadow-black);
    z-index: 5;
}

/* Responsive design */
@media (max-width: 480px) {
    #gameCanvas {
        width: 100%;
        max-width: var(--game-width);
    }

    .game-over, .start-screen {
        padding: 20px;
        width: 90%;
        max-width: 300px;
    }

    .game-over h2, .start-screen h1 {
        font-size: 2em;
    }

    button {
        padding: 10px 20px;
        font-size: 1em;
    }

    .score-display {
        font-size: 1.5em;
    }
}

@media (max-height: 700px) {
    #gameCanvas {
        height: 90vh;
        width: auto;
    }
}