Circles are circular shapes. Their width and height are locked together so they will change at the same time when either one is changed. Like the triangle and rectangle, highest value of width/height is 5000. The default width/height is 200. Rotating a circle will not affect anything. In the v1.61 update, the new inner cutout option is supposed to be used for wheels. The inner cutout, however, is only a visual change. This is a requirement of Box2D - the game's physics engine, as stated by Jim in a news post.
In the sarcastically titled HAPPY WHEELS, you have to ride a Segway, bicycle, or other vehicle through a sadistic obstacle course full of jumps, elevators, moving platforms, spinning spiked wheels, and other death traps. If you miss, you'll die or get maimed. Hit a land mine, for instance, and pieces of you and your blood will splatter everywhere. You can choose from a growing variety of characters, including Business Guy, Irresponsible Dad, and Wheelchair Guy (coming soon at time of review). Irresponsible Dad has a child in a bicycle seat, and the kid can get hurt in all the same ways as the adult character. Pop-up and banner ads are frequent, but users can make an in-app purchase to eliminate them. 2b1af7f3a8