Add a grab_point member to player.
Move default parameter declaration for displace_vehicle to prototype.
Split collision detection out into a vehicle method.
Update collision detection to allow for only detecting collisions rather than acting on them.
Add argument to move_cost methods to ignore a particular vehicle for move cost calculations.
Vehicle drag code, allows grabbing an adjacent vehicle and pulling it around with you if it is light enough.
Add new wheel type, casters.
Add a shopping cart vehicle.
Double number of parking lots.
Restyle vehicle spawning in parking lots.
Add shopping cart spawns to parking lots.