Downloaded this for my 4 year old son who likes diggers and excavators. The physics modeling is atrocious, it is possible to fly off the map literally by swiping your finger real fast across the screen. Acceleration and deceleration have no limit, and moving the excavator arm very rapidly caused it to shoot off into the sky and off the map into black space. Collision detection is nonexistent, and the sky is actually just a big dome that intersects with the ground. Inertia has no meaning in this game. Momentum is not conserved. Movement is twitchy and yet steering is surprisingly difficult. Vehicles have no center of mass or center of gravity. Very amusing in a Big Rigs manner (for those who don't get the reference, this was a computer game that was universally panned for the worst game ever made).
It is so bad it is good sort of category. If your child likes randomly flying glitchy objects, this may be the game for him/her. Or if you like to see the laws of physics just arbitrarily broken, this is the game for you. Real vehicles don't currently have the ability for spaceflight (yet). The vehicles in this app are hilariously implemented incorrectly. Physically minded purists should seek alternatives elsewhere.