Project Spark, Microsoft's ambitious creation game, was one of the more unexpected surprises of the Xbox One presentation. The free-to-play creation platform hopes to thrive on invention and shared iteration, as eager would-be developers tweak each other's creations to make full-fledged games, complete with their own rule sets and AI behaviors.

During a hands-off demonstration at E3, Microsoft showed off how quickly the tools could be used to create a functional game world. Creating the environment was the first step, made easy by a variety of simple tools. The company showed "painting" the landscape with terrain brushes using a large Surface screen, and then decorating it with environmental objects. If that method seems too time-consuming, no problem. You can chose an environment type that will cover the entire play space, or use large brushes to populate the environment with props: trees, rocks, and so on.

After that, it was time to show off the behaviors. A goblin placed near the player character was inherently violent, but switching it to a more peaceful behavior meant it would simply dance when it saw the player approaching. The developers then switched the behavior to an exploding bird, which is exactly what it sounds like: upon seeing a player approach, the goblin would start to fly away and then burst in mid-air.

These behaviors can even apply to inanimate objects. A rock, assigned to follow the player, dragged behind them unnaturally. A quick switch to the behavior, and the rock tumbled and the bizarre look was gone. Microsoft was careful to note that it's all based on the Havok physics engine, so any changes you made would respond using that game engine's underlying rule sets.

To show off the flexibility of the toolset, the company showed a fully functional keyboard that had been constructed using the basic tools. Microsoft is encouraging experimentation and iteration in the game, letting users download someone else's build and riff on it with their own twists. It cited an example of a basic blackjack game created internally, which went through four distinct stages: the basic game, a more visually fleshed-out game, the fleshed-out game with a 60-second timer, and finally, the timed game with a goblin hanging over your shoulder and giving you bad advice. It sounds awfully utopian, but I do wonder how the system will prevent people from merely taking credit for others' work.

The creation game will be free for what Microsoft calls the basic set, which was in use for creating the creation demonstration. It also noted that it will be offering new assets regularly, and that the community can feel free to use existing objects to use the assets in clever ways that fill in any gaps.

Project Spark is aiming for the launch window for Xbox One, and at some unannounced point on Windows 8 and Xbox 360. Beta sign-ups are open now, and Windows 8 will be the first recipient of the beta, if you want to scratch your creative itch.