The Spore creators have started releasing prototypes, apparently modeled on certain parts of the title's overall gameplay, and now you can download and explore the first: "ParticleMan."
"ParticleMan simulates gravitational attraction between particles in a cloud. This system was used to study such gravitational dynamics as orbits, nebula formation, star formation and particle streams from sources like pulsars and black holes," says the official site.
ParticleMan has the following elements:
• Particles - point masses which interact with each other
• Gravity Wells - fixed point masses which attract or repel particles(depending on magnitude, which can be negative), but do not move or change mass without user input
• Particle Guns - sources that spit particles out at a given angle and velocity
• Gravity Wells and Particle Guns may only be placed on the green grid in the z=0 plane.
• The Iso Surface - an isosurface geometry object derived from the positions and masses (which act as field strengths) of the particles.
By toying with the physics controls you can create different kinds of gravitational simulations. Set fusion rate to high, you can simulate the birth of stars in a collapsing nebula. Low fusion rates can simulate the interaction between stars in a galaxy.
ParticleMan is an .exe, so Mac gamers (like myself) are SOL. But if you've always wanted to make stars, and not in the American Idol sense, here's a nice weekend time-waster.
Spore Protoypes [Spore.com, big thanks to reader Bryce]