One specific but there are others: apt-get one of the doom flavors. The only one that works on my system at all is Doon-legacy SDL. It will either work as a tiny window or full screen. Using the tiny window, if the mouse is enabled as an input to the game, the cat has eaten it. No mouse anywhere else. I am running Debian 2.4.22 (Knoppix 3.3) with KDE3.1.4, I believe.