Touch Physics is a strategy/puzzle game, where the goal is to get the purple circle to touch the yellow star. As the game progresses, you are presented with an increasing array and diversity of obstacles in your path that you need to navigate the purple circle around. The circle is moved by forces of gravity, friction, and elasticity. For example, if a large object falls on the circle on the left side, the circle will move/roll/bounce to the right.
So how do you get the large object (or planks, or whatever you want)? Simple - you draw them. You get to add the objects that interact with the circle (and the rest of the obstacles, for that matter). You can draw straight lines, you can draw cirlces or polygons, just about any shape you have in mind (with a few exceptions - see below). These object are subject to the same laws of gravity, friction, and elasticity as the rest of the object in the game.
One especially cool feature of this game is that you can also adjust the various physical interactions. Increasing or decreasing gravity will influence both your objects and the movement of the circle, for example. Because of the various ability to actually adjust the physical parameters of the world, this becomes a much more interesting game - you can replay the same game multiple times with various changes to the physical constants.
This is an interesting concept for the game, and I like the interface. It looks like you are working on a simple paper background, and the images you "draw" look like they were drawn with a crayon. Settings can be changed in the settings menu (not within the game itself, one minor complaint), and there is a nice musical background that is playing as well.
My main problem with this game is the interaction - specifically, dawing shapes. Unfortunately, the game engine does not allow for the drawing of any sort of complex shapes (with multiple obtuse or acute angles, for example). If you try to draw one of those, the game "simplifies" it for you, often times negating the strategy you might have had when drawing the shape.
Other than that, however, the game is fun, and can be quite challenging. I like the interaction between what you draw and the obstacles in the way of the purple circle. I do wish you could save you progress within a level, instead of simply starting the level over, but that is a minor flaw. Shaking the iPhone to start a level over is a fun way to vent frustrations and begin anew.
All in all, this is a cool game for the money, and if you like strategy puzzle games, this might be worth your money. The interface is clean and simple, the controls are easy to learn, and the game play can be radically alterred by adjusting the physical parameters of the "universe". For $1.99 (on sale now for $.99) it is worth the money.
[Touch Physics is available from the iTunes App Store.]