He described how he designs games, and how a building a model of something can help in understanding the relationships between the objects.
To illustrate this, he described the following problem. Let's say I want to invite you to my home. I could show you a satellite map of the area and let you find your way.
But this isn't very useful. There's much more detail in the image than you need to find my place, and it gets in the way.
Instead, I could give you a map like this.
This isn't as realistic, but as a model it captures the important information and presents the relationships clearly.
When he was designing the Sims, Will started with a physical model of the environment. Little model houses on a green hilly surface with paper streets and blue water. The physical design allowed him to think about the sort of interactions that could occur in the game, before he started writing algorithms. He said that Robert Louis Stevenson took this approach with Treasure Island. First, he drew a map of the island, with places and currents charted, and then he imagined himself at each point on the island, to see what it would be like to live there. Stevenson spent three weeks doing this before he began writing.
Will then talked about game design, and how many games (linear board games, chess, Myst, Doom, and the Sims) have topologies that a gamer quickly recognizes.
For instance, a board game like Life has a linear path, with the game state explicitly displayed on the board.
Chess, however, has a tree-structure, where every move you make, and every counter-move your opponent makes, leads to a complex branching topology that eventually leads to an end.
Myst too has a linear sequence. You must solve a sequence of puzzles in order to proceed. Doom and other level based games allow more freedom, but this collapses at the end of the level (you can do whatever you want, but you have to kill the Boss, or get the key, and the new level starts cleanly from that point).
In the Sims, he wanted players to pursue a balanced approach to the game. If a player pursues a solely social or material path, they eventually reach a local maxima where they can rise no further. In order to get on to a balanced strategy, the player actually takes a hit (the yellow area in the diagram represents a lower score than the light blue) before they again progress.
It was a great talk. I'll post more from it tomorrow.
(Digg this story and read the followup)