I had a lot of fun with this game on a recent trip using DW's IPad. You build bridges using wood, steel, cables and concrete over various rivers. Each bridge has a unique material list, anchoring points and a budget. The program does a real time stress analysis of the bridge (with colored elements) as cars or trucks roll over it including a simulation of its collapse if you screwed up.
When I was in college, I would have given my left, uh, arm for a program this sophisticated.
Bridge Constructor for iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation), iPod touch (4th generation) and iPad on the iTunes App Store