body {
    font-family: Arial, sans-serif;
    background-color: #f0f8ff; /* 見やすい背景色 */
    color: #333;
    text-align: center;
    margin: 0;
    padding: 0;
}

#game-container {
    position: relative;
    margin: 20px auto;
    width: 300px;
    height: 400px; /* 高さを400pxに設定 */
    background-color: #e0ffff; /* プレイエリアも明るい色 */
    border: 2px solid #333;
    overflow: hidden;
}

#player {
    position: absolute;
    bottom: 10px;
    left: 135px;
    width: auto; /* 横幅は自動調整 */
    height: 60px; /* 縦幅固定で比率維持 */
    content: url('images/1.png'); /* プレイヤー画像を設定 */
}

#enemies img {
    position: absolute;
    transform: scale(1.3); /* 敵画像を1.3倍に拡大 */
    width: auto;
    height: 50px; /* 元画像比率を維持 */
}

#player-bullets .player-bullet,
#enemy-bullets .enemy-bullet {
    position: absolute;
    width: 3px;
    height: 20px; /* 弾の高さを2倍に拡大 */
    background-color: green;
}

#enemy-bullets .enemy-bullet {
    background-color: red;
}

#button-container {
    margin-top: 10px;
}

#start-button {
    padding: 10px 20px;
    font-size: 18px;
    cursor: pointer;
}

#game-message {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 24px;
    font-weight: bold;
    visibility: hidden;
}

.shake {
    animation: shake 0.5s;
}

@keyframes shake {
    0%, 100% { transform: translate(0, 0); }
    25% { transform: translate(-5px, 0); }
    75% { transform: translate(5px, 0); }
}

@keyframes red-flash {
    0% { background-color: #fff; }
    50% { background-color: red; }
    100% { background-color: #fff; }
}

@keyframes rainbow-flash {
    0% { background-color: red; }
    20% { background-color: orange; }
    40% { background-color: yellow; }
    60% { background-color: green; }
    80% { background-color: blue; }
    100% { background-color: purple; }
}

#game-container.shake {
    animation: shake 0.5s infinite;
}

#game-container.red-flash {
    animation: red-flash 0.5s alternate 4;
}

#game-container.rainbow-flash {
    animation: rainbow-flash 0.5s alternate 4;
}