From Jundroo, LLC:
SimplePhysics lets you design complex structures for everything from tree houses to ferris wheels to submarines and then simulates your design with a sophisticated physics engine. Create your design in seconds with the blueprints editor. If you make a mistake, simply tap the Undo button. Zoom in and out by pinching the screen and pan the view using a two finger drag. While testing, you can see how the strain is distributed across your design. Areas that are under immense strain are colored bright red, while other areas are colored green. This allows you to find and fix problem areas in your design. The finger test lets you use your finger to push and pull on your design. You can use this with pinpoint accuracy, or you can just smash your design to smithereens. The finger test has an explosive new twist. You can now create explosions by tapping the screen for ultimate annihilation.