This project consists of four pieces of code that you can use in your platform projects. MOVE lets you make your sprite move left and right. JUMP lets you, well -- jump! GRAVITY makes your sprite fall back to the ground after a jump. EXTEND STAGE lets your sprite move to a new backdrop when it reaches the limit of the stage.
This was created from scratch but uses some techniques that are fairly common. It also uses a more advanced technique to make the sprite appear to be more stable on the ground.
