Nebulon is a pretty badass looking game, but unfortunately the awesomeness doesn't translate to the actual gameplay itself. You play as a little glowing ship flying around and blasting the crap out of things. Enemies have a natural progression--their "difficulty" is based on the number of orbs which make up their ship. Blast enough of them and they'll drop powerups, which you can use to improve your own gear. Unfortunately the powerups often drop in the middle of a horde of enemies, and the movement doesn't handle quite well enough to zig and zag through more than a few enemies to retrieve your loot.
Firing your weapons depletes your energy, and once you're out of energy you'll have to just fly and dodge for a bit while things recharge. The three weapons seemed like different takes on risk/reward in relation to how often you can fire them. You can fire the basic machine guns for practically forever, but it's going to take an assload of bullets to actually kill some of the later goons. The plasma gun cuts through enemies the best, but is pretty easy to deplete. The laser is the worst gun of the bunch--it deals great damage, but it depletes your energy so quickly that you have to spend about 3/4 of your time running away from enemies while it recharges.
Should you run into anything, you'll take damage on your shields, which are displayed as little transparent-ish boxes near the top of the screen. On top of all the effects, I could barely make them out against the background--not that it matters much: the damage system makes very little sense to me. Though you have 4 or 5 shield bars, it seems as though every hit you take reduces you to one bar of shields. If already at one bar, your ship will explode and you'll lose a life.
Nebulon supports two different control schemes: dual-stick and a regular firing mode. Dual stick is apparently a more recent addition--and the only thing which makes the game even playable. The hands-down best strategy for me was "flee and shoot," moving my ship backwards while firing and the enemies which chased. In the "regular" firing mode, you can only fire in the direction you're moving (unless you cut your thrusters, which is just going to get you killed), which makes the game nearly impossible. I'm not a huge fan of dual stick shooters, but I can't imagine playing a game like this with a different control scheme.
Supposedly the most interesting thing about the game is its adaptive gameplay. Good players play against harder enemies and crappy players hang out playing the weaker bad guys. You're given a rank "Cadet", etc. as you play, and based on how well you're doing you'll rank up... a ton. I stopped counting after around 10 or 15 ranks--the highest I got was something like "Top Gun" or "Ace." Rather than discrete levels, Nebulon is more arcade-like. Based on your rank progressions, the game gets harder as you go. The problem with this plan is that there's not really any discernible difference between difficulty on adjoining "ranks," and the first dozen or so are incredibly boring.
Even in later "ranks," there are some pretty serious difficulty plateaus where I felt like I was doing the exact same thing for ages. Because the progression was adaptive, I had no real sense of "how far" I was into the experience, and thus didn't care so much what rank I was on. Had my final rank been called "Level 17" instead of "Ace," I might have gotten a bit more of that sense of progress that I was looking for. All in all, Nebulon is a great looking shooter which just isn't that engaging. It's not expensive at only 200 points, but I'd save my points for something a little more fun.