Workshop › Scorched Earth-style Artillery › Step 19 of 23

The computer aims

What we are doing

The computer aims by imagining. It tries about 17 angles × 17 powers = almost 300 shots in its head, using the same fly as real shells (with the real wind), and remembers the one that lands closest to you. Then it misses a little on purpose, or it would never miss.

```js
// The computer tries many shots in its head, picks the one landing closest to you, then misses a little.
function computerAim() {
  const me = tanks[1]
  let best = null
  for (let angle = -Math.PI + 0.2; angle < -Math.PI / 2; angle += 0.03) {
    for (let power = 4; power <= MAX_POWER; power += 0.5) {
      const s = { x: me.x + Math.cos(angle) * 14, y: me.y - 8 + Math.sin(angle) * 14, vx: Math.cos(angle) * power, vy: Math.sin(angle) * power }
      let hit = null
      for (let i = 0; i < 400 && !hit; i++) hit = fly(s)
      if (hit === 'away') continue
      const miss = Math.abs(s.x - tanks[0].x)
      if (!best || miss < best.miss) best = { miss, angle, power }
    }
  }
  me.angle = best.angle + (Math.random() - 0.5) * 0.08
  me.power = Math.min(MAX_POWER, best.power + (Math.random() - 0.5) * 0.8)
}

    computerAim()
```

What it means

The angles go from nearly flat left up to straight up; the powers from 4 to 12.
Each imaginary shell is flown frame by frame until it hits something (at most 400 frames).
miss is how far from you it landed; the smallest miss wins.
The small random change at the end makes the computer beatable.

Your turn

Above update, write computerAim with its comment.
In update, aim before the computer fires.

Skills: Velocity and gravity, Loops

← Wind Aim with the mouse →

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