Astroblast is a classic invaders type game. Your ship is positioned at the bottom of the screen, and you can move sideways and fire your cannon at the approaching invaders. The invaders move from side to side and downwards while shooting at you. If a wave of invaders reaches the bottom of the screen, it will simply reappear at the top of the screen and you get another shot at defeating them. Don't waste too much time, though, as you cannot permit your ship to run out of fuel before you get a refueling opportunity.
This game can only be played in black & white mode.