Really Slick now offers online sales of Retrobooster, their cave-flying survival shooter. The game is offered through their website, and here's a trailer from last month and here's the game's elevator pitch:

Retrobooster is a reinvention of the cave-flyer for players who love games of skill. Set at 1980s difficulty, it is a survival shooter that balances careful navigation, bullet hell battles, speed-flying challenges, and puzzles. Unlike in most cave-flyers, your ship is extremely responsive. Great detail has been invested in the physics and feel of the controls to create a fresh experience. Your first goal is merely to survive to the end, while practiced players can shoot for high scores. There is also split-screen multiplayer and a custom particle engine dishing out the pyrotechnics.