Workshop › Space Invaders-style › Step 4 of 21

Stay on screen

What we are doing

The ship must not leave the screen. After moving, its x is kept between 0 and the canvas width minus the ship's width.

```js
ship.x = Math.max(0, Math.min(canvas.width - SHIP_W, ship.x))
```

What it means

• Math.min(canvas.width - SHIP_W, x) stops it at the right edge, Math.max(0, ...) at the left edge.

Your turn

At the end of update, write the line.

Skills: Game states

← Move the ship Fire →

All steps

1. The ship
2. The game loop
3. Move the ship
4. Stay on screen
5. Fire
6. Bullets fly
7. A short reload
8. The invaders
9. The march
10. Hit!
11. Score
12. They shoot back
13. Bombs fall
14. Lives
15. Game over
16. Best score
17. A wave in a function
18. Play again
19. Waves
20. Faster and faster
21. Build it yourself: an extra life