Cosmic Crusader

Cosmic Crusader is to Galaxian as Space Strike (by the same programmer) was to Space Invaders. An alien space fleet has discovered the location of Earth, and - being an alien space fleet - immediately sets out on the attack. The only thing standing between the enemy and total Terran termination is you - the player, with your puny gunship that's stuck to the bottom of the screen and can only move left and right.

Each stage pits you against a contingent of alien ships hovering menacingly above you. Occasionally, an enemy will break formation and go out on a sortie, diving towards you while shooting - only to re-emerge at the top of the screen. The different ship types have different offensive maneuvers. Shooting them in the midst of a dive scores more points than picking them off in formation; some will bring their buddies along and go out in triads, which net you a special bonus if destroyed in the right order. Another bonus is awarded for eliminating the command ship that comes along once per level, shoots at you and runs off.

You can temporarily protect yourself by activating your shields (at the cost of your ability to fire) - knock down the occasional floating disc to get an extra one. You start with three ships, and gain a new one for every 2000 points scored. 9 difficulty levels are available.