为什么我的敌人的健康条在与子弹相撞后不能缩小？

function checkCollision(bullet, enemy) {
    return bullet.x < enemy.x + enemy.width &&
           bullet.x + bullet.width > enemy.x &&
           bullet.y < enemy.y + enemy.height &&
           bullet.y + bullet.height > enemy.y;
}

function updateHealthBar(enemy) {
    enemy.health -= bullet.damage;
    if (enemy.health <= 0) {
        enemy.health = 0;
        // 处理敌人死亡逻辑
    }
    // 更新健康条显示
    updateHealthBarDisplay(enemy.health);
}

function updateHealthBarDisplay(health) {
    const healthBar = document.getElementById('health-bar');
    healthBar.style.width = `${health}%`;
    healthBar.style.backgroundColor = `rgb(${255 - (255 * (1 - health / 100))}, 0, 0)`;
}

const bullet = {
    x: 100,
    y: 100,
    width: 5,
    height: 5,
    damage: 10 // 确保设置了伤害值
};