This is not a game. This is an experiment.
It's kind of complicated, so I'll do what I can to explain it. Basically, that number down the bottom in the parentheses (brackets) is the cars goal. The game will randomly generate a car that consists only of triangles, boxes, and wheels, and that car will attempt to reach the goal. When it either reaches the goal or fails, it disappears and a new car is generated. In total, 19 cars are generated and tested. Then we go onto Generation 2, where the system will take the most successful of the cars from Generation 1, and combine attributes (things like wheel count/position, shape) of them to make the new 19 cars for Generation 2, which will again try to reach the goal (the goal will be higher now). This goes on infinitely, as the system tries to create the perfect car.
You can also turn up the mutation rate (in the bottom right) which gives the system a chance to make cars have strange attributes that weren't in the previous generation. The last thing you can do is vote a car up or down, which will increase/decrease the likely-hood of that car's DNA being used for the next generation.
http://www.boxcar2d.com/

Evolutionary algorithms at its finest.

Certainly. Try leaving it on overnight and waking up to find a kickin' rad car that travels into the thousands.

This is amazing thanks for sharing!

It's fun to watch.

There was one time it generated a car with no wheels whatsoever. Believe it or not, it actually got a score of 2.4.

There are threads about this all over /b/ at the moment, with people posting screenshots of awesome cars they've gotten.

Who made this, by the way?