I used to play a similar game years and years ago[1]. It's very easy in the beginning, but you quickly reach a point where it becomes very, very hard. I think I never reached level 20, but it doesn't matter, it's addictive, it's challenging, even if you don't go so far in the game you replay and replay until you beat one more level.

[1] http://www.play4traffic.com/game.php