Turns out that the array scheme I proposed in my previous diary entry won't work. One of my early goals was to give the aliens free-rein of the screen, rather than being confined to fixed rows. Therefore, my options were more limited in how to avoid aliens shooting through each other. So I currently have each alien check below himself for the presence of other aliens before firing. That scheme seems to play fairly well. Since it's a slow step, I'm not gonna constantly allow all aliens to fire. For each step I'll probably just randomly ask a few aliens if they wanna fire. If they're clear and have a good shot, they'll fire. That way I can also put the firing AI into each invader. Some will fire whenever they've got a chance. Some will wait until they've got a bead on you.
I'll probably do the invader AI similarly to the way I did it in Think Tank. Every enemy is given a random number at the onset, from 5 to 50. If an alien's within that many pixels of you in the X direction, he's likely to fire. It worked out very well in Think Tank, as not all of the tanks had firing capabilities. You didn't know if one was gonna fire at you until you were in its sights :)
I think I've already figured out the next game I'll write. It's gonna be a version of Shi Sen tile solitaire. It's one of those Mahjongg-tile solitaire games, but the rules are quite different from the other ones out there. There are a couple of versions in Java on the web, but they're not very good and they're not in English. I figure that an English version with a few good options could be a winner.
Completion of Shi Sen, amazingly enough will be the completion of game number 12 in my attempt to complete a new game pack and get it on the market before Christmas. Looks like I might make it.
As a bit of trivia, this whole developer diary started out about midway through Zap Pod! I've written seven games since then; working on a pace that would make Roger Corman proud. Hopefully I'll have time to clobber bugs and add enhancements before it's ship-time.