Just bought this game -
Girders. It brings back memories of freshman year in HS when I played around on a CAD program that could design bridges. It's a lot of fun that gets the engineer in all of us going.
The bridge mode is kinda short, but it's a LOT of fun if you enjoy using your brain. Tower mode is going to be a lot more challenging.
Buy it from handango, since you can use the SEPTSAVINGS and get the price down!