No pieces can be taken. Kings cannot escape direct check (or a check on an adjacent square) The only rule is that pieces swap squares when they 'capture'. THe game is extremely easy to lose but incredibly beautiful for the different kinds of positions that can arise. Here's a video

http://www.youtube.com/watch?v=OeozKSV8u0E&list=UUyKO7sBrymJO6e8Ik9q9nHw&feature=plcp