~ MR. HELI ~
I like some of the ideas Irem came up with for this game. Instead of zooming along in one direction like craft do in most other shooters, your Heli is kind of a "free roamer," as he's able to look around for secrets and blast up rocks to reveal hidden crystals or power-ups (which can be bought with the crystals, introducing a wee bit of strategy).
The gameplay feels pretty good when you're fluttering about with spread fire and multi-missiles, and it's fun to stumble upon obscured niches in the environments.
Contrary to what you might expect from an Irem shooter, you can wing your way through almost every part of the game without bothering to memorize anything, as most of the enemies offer very little in the ways of pursuit and resistance. In most places, it's easy enough to flee from your foes if you're low on power and not a problem to bust them up if you're high. (It's worth keeping in mind that you're occasionally rewarded for facing and defeating tougher enemies rather than flying away.) While you're cruising along, you'll just need to keep in mind that there are a couple of spots where you can get killed in the blink of an eye if you're not being careful.
Although the game does rev up the capabilities of the enemy forces if you're powered up and doing well (a shooter methodology I always call bullshit on), things are easy enough that it's not really much of a concern except in one or two instances (the fifth mini-boss in particular goes from being a church mouse to a demon if you confront him at full strength).
While the game is a bit of a fan favorite, there are quite a few things I don't like about it. Everyone loves the orange 'copter, but I find him annoying, as I hate chubby hitboxes. The primitive graphics are just a small step above NES quality, while the music that I've actually noticed is cutesy, twinkly, lullaby-like crap (except for one brief sinister part of the last level's theme, which is cool).
The slowdown in spots is atrocious: calling to mind Rayxanber II, there was a time when I was in the fifth level with full fire and a lot of enemies about, and the slowdown became so bad that my gun stopped firing. (Thankfully, the ol' Ray II trick of placing the turbo switch in the middle position works here as well.)
Speaking of slowdown-ridden stretches, players must endure some extremely stupid "find the door in the empty dark room" parts that seem to have no point whatsoever except perhaps to show the pathetic degree of slowdown a PCE game can exhibit when there aren't even any enemies present.
Those who persist through the mire will at least get to partake in some worthwhile end-of-level showdowns. While we're not talking rocket science here, most of the bosses do demand that you think a little in order to come up with the most effective methods for beating them. The thought-provoking duels account for most of the enjoyment I get out of the game.