Hacks (or cheats) are changes in a game's coding which can be manipulated by the player to perform actions that cannot be executed throughout normal game play. Hacks take advantage of these changes, and can sometimes completely alter the game play for the player. Hacking can be done by using a system to run with the game of choice to hack such as Game Genie, Action Replay, Pro Action Replay, or Gameshark. A number of hacks can be found in various Mega Man titles.