Interesting concept. --- I had made up a version of chess and had referred to it as "echo chess". Guess I'll need a new name. I'll go with "Afterimage". It is normal chess with white/black pieces, but you also have a set of extra pieces kept off to the side. (preferably glass/frosted glass 'ghost-looking' pieces) - When you move a piece, you place a glass copy of that piece in that prior spot. - The glass 'afterimage' piece only lives for a single turn and it is removed after you make your next move at the moment you would be placing another glass 'afterimage' piece down of the piece you move on that turn. - The 'afterimage' piece cannot be moved, but it also cannot be moved through or captured. There are more difficult variations I made where the piece can be moved, but only so far before it 'fades', as well as a version where capturing the 'afterimage' causes limitations or changes to the parent piece, or even capturing-by-proxy if the 'afterimage' of a piece is captured twice. Seemed fun to me, but I always played it against myself as I could never get anyone to even want to try playing it a single time.