Structural Engineering Challenge is a very good shareware game that simulates custom-built truss structures under load.It is basically a more serious and less accessible simulation than Pontifex, being designed with students in mind. Short description from the official site: "You are asked to design a series of structures (approximating to real life situations). Each structure must support the required loadings and only use the predefined foundation areas for support. Certain areas of the screen must be avoided (representing obstacles or non-loadbearing soil perhaps). Structures are put together by dragging and dropping members on a rectangular grid on the screen. Structures can be assembled in a few minutes. Many different configurations can be quickly investigated. The program has been designed with students and other interested parties in mind.

The program will load-test your structure in a progressive dynamic way, showing deflected shapes and allowing you to track its progressive collapse. You can view the member loadings and numeric deflection values at any point in the simulation. The efficiency of your design configuration will be determined by calculating how much weight of material would be required to carry the specified loads."

With a strong underlying physics model, Structural Engineering Challenge is ideal for engineering students or Bridge Builder/Pontifex fans who want to try a more realistic simulation of bridges. The learning curve is somewhat steep, but fortunately the documentation and tutorial are both very well-written. With the ability to create new challenges on your own and new ones being posted regularly at the official site, Structural Engineering Challenge is a strong simulation with considerable long-term play value. Well worth the small registration price tag of $12. Highly recommended!