So I've grabbed that Cryptark game, and...
....honestly, I think this one might have alot of examples of things NOT to do in this game, and also examples of things that'd do this game justice. Since I think it's a very good example of many concepts, I figured I'd go into it a bit:
Negatives first, because it's me doing the posting here:
1. Enemies blend in with everything else, due to the game's absolutely awful color scheme. It's YET ANOTHER "there's only two colors in the visible spectrum" game. Which in this game is "Green, and slightly different green". Very, very bad idea. You're GOING to get hit by things you cant see, because they look just like the level structure. Every single enemy I've encountered has this issue. *ALL* of them. Only the major "systems" look different (all of those are purple). For the love of all that is good and kitten-shaped, this needs to not happen in this game. It's one of the worst mistakes that can be done in anything with shmup elements. The good thing is that bullets stand out well enough, but there's lots of physical attackers in here, or turrets that arent meant to be stealthy, but that you just wont notice till they fire at you.
2. Threats are numerous, but weapons are weak as heck. It's not so much that this increases difficulty; it's that it increases tedium. Things just take too long to kill, which means even an easy battle will drag out too long. Isaac actually has this issue sometimes... the game makes up for it in that the rest of the game is just so GREAT that this one isnt too bad in comparison... and of course, you wont encounter this one on every run because of how character builds work. BD can also have this issue.
3. Ammo. Holy exploding penguins, Batman, do I ever hate it when games of this type use ammo systems for basic weapons. This one is kind of subjective, but I cant stand it myself. It doesnt ruin the game, but it's VERY obnoxious.
4. Doors that make no sense. Like, locked doors that you can just go around by going around a very nearby corner, or ones that block off a corridor so empty that there arent even enemies in it. If you've got a locked area in a game like this, there needs to be something important behind it, always. Give the player some satisfaction after opening every locked thing. Well, you could also give them a trap at times, which is at least something.
Now, dont get me wrong: as negative as I sound here, well.... I always sound negative, and this game is still pretty good. But these are all issues that are pretty easy to avoid, and I think they should be focused on a bit during testing and balancing. There's some things I really like here too, that are good in any game of this type:
1. Objectives to go after. In this game, it's the "systems" that are found througout the ship and are marked on the map. Every one of them does something INTERESTING and important, and choosing what to go after first is a pretty big decision most of the time. That "tough decision" process is great for games like this. Isaac is one that does this well... there's alot of different special rooms to find in there, and making decisions on which ones to go after first, and which ones you should be using your limited keys on, is very good for the game. Nuclear Throne on the other hand, good as it is, DOESNT do this well. Levels in that are kinda boring; it's all about having things to shoot instead. The actual structure doesnt matter yet at all.
2. Combat can take too long, as I said, but it's still fun and exciting. Enemy patterns are a little on the uninteresting side, but there's always something to shoot at, and clearing out an area is satisfying to do. Arcen's games actually tend to already be pretty good at this, so I think this aspect should be easy to manage for this new game.
3. Side goals. What gets me about these is that not only do they give you a money bonus when completed, but they're also actually INTERESTING. And they tend to be dangerous... deciding wether you should really try for a specific one can be difficult. Managing to do one is satisfying, and can get you more STUFF. Stuff is good, everybody likes stuff.
4. Huge mazes to explore. Ya GOTTA have exploration in a game like this, and big complicated areas really help. For Arcen, BD is the game that does this the best, I think. Well, so does AI Wars, for that matter, just in a very different way.
So that's some thoughts on the design of that game, and how it might be applied to the concepts and decisions in this game. I dunno how much of that is particularly useful, but I figured I may as well go into it a bit regardless, in case it can bring about a bit of inspiration or help prevent problems.