Driving feels right with three different rates: up accelerates, down brakes much harder, and letting go coasts, slowly
losing speed. And there is a top speed.
```js
const MAX_SPEED = 120 // world units per frame
if (keys.ArrowUp) speed += 1.2
else if (keys.ArrowDown) speed -= 3
else speed -= 0.4
speed = Math.max(0, Math.min(MAX_SPEED, speed))
```
What it means
if ... else if ... else: only the first true branch runs; else runs when no key is held.
Math.min(MAX_SPEED, speed) takes the smaller number, so the speed never goes over the top; Math.max(0, ...) the
bigger, so it never goes below 0.
Your turn
Under the DRAW line write MAX_SPEED.
In update, under the ArrowUp line, write the three new lines.
Skills: Velocity and gravity, Keyboard and mouse input