We're going to make a very basic physics simulator: We'll simulate something falling. Keep your Scratchy sprite because we're going to do some testing on him.

1. Add two new variables: y-pos which stands for Y-Position and y-speed which of course means Y-Speed. These will represent the vertical position and speed for Scratchy, respectively.

You're screen should look something or other like this.

2. Copy this code for Scratchy's sprite.

What this code means is this: If our buddy Scratchy is actually on screen (above y=-123) then decrease his y-position (i.e. make him fall) by a rate of y-speed (the rate he falls).

Click the green flag and try it out. If he goes off screen, click the orange set y-pos block to reset his position back to 0.