Are you a fan of the classic first-person shooter Doom game? If yes, you are in luck.
In case you are new to this game - it's very simple. Just kill the monsters in your path while moving from one room to the other. Clue: search for the "Exit" sign.
After searching on net for a while, got this version on Takegame.com, which is totally free. Just download into your computer and you are all set to go kill some monsters.