The basic idea behind Crayon Physics is that gamers have to get a ball to a point that is marked by a star. This is accomplished by drawing a number of different items that can act in a variety of ways to help get the ball from Point A to Point B. On a basic level, the drawings act as ramps or barriers, while more advanced implementation accomplishes a number of feats like creating weights and levers, as well as malleable platforms that can be affected by other creations.
What makes Crayon Physics so entertaining is that there are a number of different ways to solve each level, thanks to the fact that no one is going to draw the same things in exactly the same way. It requires players to be creative and solve each puzzle through whatever means they can conceive, as opposed to only having one convoluted method as the only solution.
However, the most powerful thing about the game is its charm. The visual presentation is meant to look like a folded up piece of paper that a child has been doodling on with crayons. Not only that, but the soundtrack is extremely unobtrusive and soothing.
From the Crayola Physics Deluxe website
Crayola Physics Deluxe is a 2D physics puzzle / sandbox game, in which you get to experience what it would be like if your drawings would be magically transformed into real physical objects. Solve puzzles with your artistic vision and creative use of physics.