physics.cs

public class Collider : Spatial {
	private Enum ColliderType { Box, Sphere, Capsule };
	public virtual float GetArea(ColliderType colliderType) {
		switch(colliderType) {
			case Box:
				// return area of box
				break;
			case Sphere:
				// return area of sphere
				break;
			case Capsule:
				// return area of capsule
				break;
		}
	}
}

public class RigidBody : Collider {
	public Vector3 velocity;
	public float mass;
	public float drag;
}