Bit.Trip is a series of video games developed by Gaijin Games and published by Aksys Games for WiiWare. Each game revolves around the adventures of a character named "Commander Video", and features "a crazy mix of 80s aesthetics and modern game design". Each game in the series features a chiptune-inspired soundtrack, but a different style of rhythm-based gameplay in each. Beat, Core, Void, and Runner each contain three distinct levels, each one ending in a unique boss battle. Most bosses are based on various games and game genres from the early Atari era. Six Bit.Trip games are intended to be released in total.
Source: Wikipedia, "Bit.Trip," available under the CC-BY-SA License.