Invadder (UK) (19xx) - Amstrad CPC - Shooter, Arcade

This shoot-em-up is in fact intended to practice math addition. The game opens with aliens descending the screen. They carry a random number. You must shoot enough aliens to reach your 'target score' but if you are touched by alien or if you exceed this score,you lose one of your three lives. Beware, if you shoot an alien which carries a zero the score falls to zero. To obtain carried points you must to destroy him in one go.