Players need to see how the fight is going. A health bar is two rectangles: the full width in dark red, and on top
a green part as wide as the health that is left. Each enemy now remembers its maxHp.
```js
enemies.push({ d: 0, hp: 10, maxHp: 10 })
// Health bar: red underneath, green for what is left.
ctx.fillStyle = '#7f1d1d'
ctx.fillRect(x - 14, y - 20, 28, 4)
ctx.fillStyle = '#22c55e'
ctx.fillRect(x - 14, y - 20, (28 * e.hp) / e.maxHp, 4)
```
What it means
hp / maxHp is a fraction from 0 to 1, so the same line works for weak and strong enemies.
The bar is 28 pixels wide and 4 tall, 20 pixels above the enemy's center.
Your turn
In update, add maxHp: 10 to the new enemy.
In draw, at the end of the enemies loop (under ctx.fill()), write the health bar.