Developer: Charlie Heath

Charlie Heath, the designer of Reactor, also programmed games for Activision. The site has his unreleased Activision prototype Thwocker from 1984, described as “Joust with musical instruments”: a bouncing conductor collects notes through a maze to build a song. Heath has said it was about 80% complete when it was cancelled. A copy turned up in a thrift shop in 2001.
Give the prototype a try below, in your browser.