?: number How much velocity decays (velocity *= (1 - drag) every frame).
?: number Initial speed in pixels per second for jump().
?: number Maximum velocity when falling.
?: boolean If object is static, it won't move, all non static objects won't move past it, and all
calls to addForce(), applyImpulse(), or jump() on this body will do absolutely nothing.
?: boolean If object should move with moving platform (default true).
?: number Mass of the body, decides how much a non-static body should move when resolves with another non-static body. (default 1).