I seldom see this fine little shooter mentioned on the forum, let's change that!
Anybody ever play Mr. Heli? I love how unconventional it is...kinda like a more polished Atomic Robo Kid.
The basics are that you freely navigate the level, and shoot the crap out of rocks everywhere. Crystals from the rocks can be used to buy hidden weapons and health. Each level also has vertically autoscrolling segment, and an underground level before the boss.
Certain bosses scale in difficulty depending on how powered up you are.
Nice environmental destruction, level design, and magical tunes. The art style is also really good.
There's also a hard mode (3 hit death) like the arcade version...never got too far. The PCE mode is pretty easy to 1CC once you play it enough though.
I think the only flaw is the slowdown in the "underground" levels...but overall it's honestly one of my favorite games period. Might be the nostalgia talking.
http://www.thebrothersduomazov.com/2009/04/mr-heli.html Decent summary