Ataxx is the real original game by the authors mentioned at the Assimilation rules. Due to a former misinterpretation of the rules, this one was added after Assimilation. There is only one (but important) additional rule:
A piece can be moved 2 spaces in a L-shaped jump, identical to a knight move at Chess. This move causes no duplication, the piece is really moved and disappears from its former position.