OrangePixel's original Groundskeeper was more of an experiment than a full game, an endless survivor-shooter in the company's typical old-school 2D style. The sequel retains the look and feel, but everything has been expanded: there's now a full story behind the tiny compartmentalized levels, you have access to a staggering amount of weapons, and the graphics and on-screen action have been given a considerable boost.
The game features the developer's usual calling cards: retro basics dialed up to 11. At the core it's a Contra-style shooter, but the sheer chaos of dozens of enemies and attacks on screen at once combined with impressive speed means it also has a bit of "bullet hell" DNA as well.
If you're a fan of action games and nostalgic 8-bit throwbacks, then OrangePixel's new title Gunslugs should be right up your alley. Featuring the NES-style graphics that OP is known for, alongside non-stop bullet-blazing action, Gunslugs in an adrenaline-fueled homage to the 80s action heroes of old.
Gunslugs also throws a unique spin on the traditional platformer: it generates the levels randomly. Basically, that means levels will appear in a different order every time you play. Neat, right? Aside from that, it features unlockable characters, a badass chiptune soundtrack, tons of weapons, tanks, and jetpacks; secret levels, all sorts of other fun chaos.
Orange Pixel, creators of the well-received "Meganoid", just released a platform/shooter called "INC".
There are 40 levels of robot blasting action, and 8-bit styling and sound effects. It's sort of like Mega Man. The description claims "hard-but-fair gameplay," so there's retro difficulty to go along with those retro graphics. Xperia Play owners will be glad to hear that all their fancy buttons are supported (like you couldn't tell from the giant video thumbnail).
8-bit shooters don't really need a story, but just for good measure: "[In] The year 2135, the world is ruled by Corporations, humans are slowly being replaced by robots and machines, and the most powerful humans are now looking for ways to transfer their souls into robots, for eternal life." TL;DR: "Shoot things.