Centipede on the IBM PC programmed by R.J.Grafe in 1983. It's not the official port by Atarisoft but another release sporting quite an innovative control scheme. It actually features a simulation of the trackball found on the original arcade game. It uses the space bar for firing and the cursor keys to move around the little gun-turret. Pressing a directional key is similar to giving the trackball a swirl. Pressing multiple times in rapid succesion is like giving the trackball more momentum. A bit of an indirect control scheme but it really works well. With this control scheme in place this actually makes for an excellent port.
Take a look at the video and see how I fared.