body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: #f0f0f0;
    overflow: hidden; /* スマホでのスクロールを防止 */
}

#game-container {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    padding: 20px;
    text-align: center;
    width: 100%;
    max-width: 500px;
    box-sizing: border-box;
}

h1 {
    color: #333;
}

#score-display {
    font-size: 1.5em;
    margin-bottom: 20px;
    color: #555;
}

#start-button {
    background-color: #007bff;
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 1.2em;
    border-radius: 5px;
    cursor: pointer;
    margin-bottom: 20px;
}

#start-button:hover {
    background-color: #0056b3;
}

#game-area {
    border: 2px solid #ccc;
    width: 100%;
    height: 400px;
    position: relative;
    overflow: hidden; /* うなぎがはみ出さないように */
    background-color: #e0f7fa;
    touch-action: manipulation; /* タッチイベントの遅延を防止 */
}

.eel {
    position: absolute;
    width: 20px;
    height: 100px;
    background-color: #4CAF50;
    border-radius: 10px;
    cursor: pointer;
    display: none; /* 初期状態では非表示 */
    animation: eel-wave 1s infinite alternate;
    transform-origin: bottom; /* 下を起点に波打つ */
    left: var(--eel-x);
    top: var(--eel-y);
}

@keyframes eel-wave {
    from { transform: rotate(-5deg); }
    to { transform: rotate(5deg); }
}

.eel.visible {
    display: block;
}

.eel.hit {
    background-color: #ffc107;
    animation: none;
}