While we're discussing shooters: Nanostray on the Nintendo DS is hard core. Shin'en, the developer, has stated that the Normal mode of this game is really the Easy mode renamed. That said, it's still not "easy" by any stretch of the imagination, which is probably why they renamed it. I beat it in a couple of hours on that setting, but it handed me unlimited continues and didn't unlock anything. The medium difficulty mode gives you 5 credits with 5 ships each, and the hard difficulty only hands out 3 ships for each of its 3 credits. You also take more damage at higher difficulties, which means that it ramps up substantially.
I don't understand why there are so few shooters made for portable systems. It seems to me like they're perfectly suited for it. After all, on a console I can't play them for very long--the repetition and the harsh gameplay gets frustrating after a while. But on a handheld, I'm probably not going to be playing for long periods of time anyway. Nanostray, unlike its predecessor Iridion II, does have a battery save, so you can stop at just about any time. And the challenge missions, which include limitations or artificial goals to meet (no smart bombs, 35,000 points, no secondary weapons, etc.) are a good way to jump in, spend a few minutes, and maybe be rewarded with one of the game's unlockable features. Not that I've managed to do so yet, because Nanostray is hard core.
The perspective isn't completely top down, but it might as well be--the "tilt" is largely an optical illusion and rarely interferes with the gameplay, although it does come into play during a couple of the boss encounters. A more serious problem is the button mapping. There are four non-upgradeable weapon/subweapon combos available at any time during a level, but to switch between them you have to tap the touch screen. I don't necessarily have a problem with that, but to make it work the developers have copied the fire button to the left trigger (normally on A), so you can continue shooting while you change weapon types. That makes my hand cramp up a little sometimes. It would be nice if they'd just included a next weapon function on the Y button, which isn't used. Also, the bottom screen's 2D graphics (radar, health, and super meter) are very pretty, but I'd like them to have been higher contrast so I could see them more clearly in my peripheral vision.
Regardless, these flaws don't make Nanostray a bad game. In fact, it's a pretty good example of the type, and with the current dearth of portable shooters we have to take what we can get. If you can find a copy (several stores won't carry it for some reason), it's well worth the trouble.