All great platformers have animated heroes. Even Super Mario, which was released in 1985, used several animations for the player. Why? Because it would look completely unrealistic if Mario just stood frozen in one animation while he runs and jumps around the level. So it makes sense that we should add animations to our player. This will add yet another step of realism to the game.
Try running, jumping, or standing still. See how the player’s animation state reacts:
My art could definitely be improved, but I’ll demonstrate how to create these 3 animations for simplicity’s sake.
The Structure
The most important aspect of giving any game element multiple animation states, is to make sure you structure it correctly. When I first started programming, I tried to put all of the animations on a single timeline, and the resulting structure was too cluttered and complicated that it was difficult to make things work the way I wanted them to. So now I’m sharing with you a simpler method.
AS3 Game Tutorials 