Make it move

The stage isn't a vague white area — it's a grid, and every point on it has an exact address made of two numbers:

• x is how far left or right (−240 on the far left, 240 on the far right)
• y is how far up or down (−180 at the bottom, 180 at the top)

The centre is x: 0, y: 0.

This is the same grid from your maths class, and the same idea as the robot grid from Chapter 2 — only now the computer tracks the position for you.

There are two completely different ways to move a sprite, and mixing them up causes a lot of confusion:

• move 10 steps moves relative to where it is now — ten steps forward from wherever that is, in whatever direction it faces.
• go to x: 0 y: 0 moves to an absolute address — the centre, always, no matter where it was.

Use relative movement for walking and gliding. Use absolute movement for resetting, spawning, and sending something back to the start.