Hexago is a variant of Go played on a hex grid (of undefined size and shape, although an overall hexagonal shape for the board is suggested). Stones are played on the spaces, not the intersections. The rules are a bit different from those of Go. Hexago has no ko rule and no cutting. Most importantly, players cannot pass, and in fact are required to fill in their own eyes if no other moves are available. The rules were published in Games & Puzzles #5 (September 1972).