you can upgrade simple car to a whole new level with power functions.
The motor is just added instead of the handle and the battery box is stuck on top.
How to build it yourself
Build simple car - it is at http://bostonsbrickcloset.blogspot.com/2015/11/simple-car.html
These are the parts you will need in addition to the parts from simple car.
Then watch this "Build with Boston" tutorial.