Build your bridge with love. Be proud of your creation, and give it a pompous name. Then eventually watch it with horror collapsing as a train runs of it, giving you an undeniable proof that your bridge was indeed flawed. Then start over.

These few sentences depict well a typical game of Pontifex, the successor of the infamous freeware Bridge Builder which had already made crazy numerous players around the world when it was released.

As its name suggests, this game is all about building bridges. Each level confronts you with the same challenge: there is a river to cross, and it's up to you to devise the bridge. Three materials are available - light steel, heavy steel and wire - each with own strength, weight and price. In order to clear a level, your bridge must be able to withstand successfully the weight of a train running on it. Hopefully, you can try an unlimited number of times...

The game actually features a very advanced physics model, taking into account compression and stretching - and of course gravity.