Seamus's physics system was really ahead of its time, but unfortunately a ton of the work of getting a physics system to work in a real game is dealing with edge cases, numerical stability, etc., and we had huge problems getting everything to an industrial-strength state. (You will probably not be surprised if you look at the code.) Terra Nova: Strike Force Centauri's full biped physics eventually had to be replaced by run-of-the-mill sphere physics just to make sure that things worked 100% of the time instead of 95%. Flight Unlimited was the real culmination of Seamus's physics work.