Call player 'circle' instead of 'shape'.
Add a floor-like rectangle.
Add class Player.
Use Player class instead of velocity and circle.
Move controls into player class.
Move ancillary detail into Player class.
Enable arrows and slightly abstract controls.
Try a switch instead of an if for the event poll.
'Update' velocity sounds better than 'change'.
Update velocity using its vector instead of its components.
Use sprite for player instead of circleshape.
Excise unused geometry class.
Tell player to draw itself.
Pull position update into Player class.
Add rudimentary object intersection.