Applying recent techniques for retro games: in the case of undo function

Emulation is one of the most important methods for providing lower compatibilities, and several game machines truly adopt emulations. A game emulator establishes executions of the games of its target machine. At the same time, when we append a new function on an emulator, we can apply the function for all games on the emulator. Actually, many game emulators adopt extra functions and we gain many benefits from these functions. These functions sometimes bridge the gaps between recent games and retro games. However, these functions leave rooms for improvements.We implemented and evaluated undo function as an example of the improvements. This function removed the problems of the traditional function, and achieved performance gains from the traditional. Except when we fully engaged in the traditional function, our function considerably reduced the penalties of the failures in games. In addition our function also homogenized the penalties without dedications. We can use our function easily and safely.