Deep Blue is a garbage shoot 'em up that's often considered one of the worst games on the TurboGrafX-16. It deserves that reputation. But the way it handles damage is unique for the genre. It's the only shmup I know of where you have regenerating health. This only happens when you're not shooting, a mechanic that theoretically could lead to interesting choices like "should I take a risk and keep going for score even though my health is low?" or "Is it worth waiting, or would it actually be safer to take that boss out as fast as possible?" But it doesn't work great here, as you're just constantly bombarded by enemies moving in sin wave patterns, and it's hard to actually avoid them for long. And it's not communicated as well as you'd hope: you don't have a health bar, with your health instead being shown by the color of your fish's eye, and what causes it to recharge isn't obvious just by playing the game. There's one old guide out there where the author thought you healed by mashing the start button (which I guess technically works, since you'd probably take your hand off of the fire button to do that).
Still, ever since I played this, I've been wondering what we'd get if a more competent developer made a shmup with a health mechanic like this. If there's one out there that I missed, let me know.
