James Vernon (http://www.ticalc.org/archives/files/authors/57/5713.html) has just released two wonderful games for the 83/4+, Invaded (http://www.ticalc.org/archives/files/fileinfo/446/44687.html), a side scrolling shoot-em-up, and Alien Breed IV (http://www.ticalc.org/archives/files/fileinfo/447/44709.html), the conclusion to his popular series.
Invaded features many different enemy types, bosses, fun terrain, and a few other things. The most notable feature of all, however, is a powerup called "the Orb". the Orb can be attached to one's ship on either front or back by simply running into it, and detached again with alpha. when attached, it acts as a shield against weaker bullets, while leaving it on its own causes it to fire at the same time you do. you can also pick up weapon bonuses which increase the blob's power, giving it different weapons while it is attached or the ability to fire four bullets when detached. altogether, it makes for a pretty unique experience.
oh, and it includes a custom level editor as well, written for windows machines. ;D
(http://img.removedfromgame.com/imgs/inv83p.gif)
the second of James' two games, Alien Breed IV: Final Assault, is a top down shooter. there are separate objectives for each level, but the basic premise of the game is "to blast away as many of the aliens as you can to save the Human race." it has a pretty full feature set, including clean, four-way smooth scrolling maps, interactable map elements, different weapon types, a radar, alien spawning pits, multiple enemy types, one way doors, time limits for certain areas, and more! the enemy AI is a bit basic, but with that many enemies being simulated at once i'm not going to complain. check it out!
(http://img.removedfromgame.com/imgs/ab4.gif)