Straight out of grad school I was really lucky to go to work for the game developer Harmonix, which was then a small independent game developer, on a then small project. Turned out to be the first game in the now rock-start status franchise Guitar Hero (the one with the plastic guitar).
My contribution on Guitar Hero 1 was to help author the levels of the game, provide general game design input, and design the multi-player mode, which required tuning the difficulty levels and game details in a way that reached a wide swath of ability level.
While working at Harmonix I also prototyped several new music game concepts for devices like the PSP. And helped with the game prototype that eventually turned into Phase for the iPod.
