X.Tron

Xtron is a dead average Space Invaders clone by Keypunch - one of the first commercial clones of its kind. Nothing more to say, really -- if you like Space Invaders, this is a competent clone that will give you the same gameplay, although not necessarily addictiveness: the gameplay is very repetitive, and there are few surprises in store to keep you playing.

Worth a look only if you collect games of this type, or if you are somehow a fan of Keypunch's games - this is one of the rarest from them. Given the game's lackluster quality, I'm not surprised it is very hard to find ;)