Fans of 6DOF games aren't exactly spoiled for choice. In the 90s, there's been Descent and Forsaken, whereas these days, there's Overload, Desecrators, and Sublevel Zero (SLZ). The latter two have another thing in common, which are procedural levels. Given that SLZ is run-based, resorting to randomized levels is a sound choice, but variety unfortunately is lacking. By the second run, you've likely seen all the assets, and the level design always follows the same pattern: If the path branches, one of the branches will lead to a challenge room and possibly include a keycard, whereas the other one takes you to the stage boss. These boss rooms are always the same, too, and after five runs in total you'll also have pretty much everything unlocked. In short, SLZ isn't a particularly lengthy or deep game.
At the same time, the base gameplay loop is plain enjoyable. Flying around and shooting stuff feels great, the enemies all have different movement and attack patterns, and there are even some minor RPG elements, as enemies drop new hull, engine, and weapons modules, which can be combined to create new and better parts. Trying out new gear is always fun, and the game is easy enough to allow experimenting.
Visually, SLZ is rather minimalistic in terms of textures and colors, which is contrasted with heavy bloom effects, though these can get a bit excessive at times. All weapons have satisfying sound effects, and while the soundtrack is more calm and collected than upbeat and driving like Forsaken's, for instance, I enjoyed listening to it throughout. In terms of bugs, I've had an instance where one of the challenge rooms didn't properly unlock, which necessitated a level restart, but other than that, it's been smooth sailing.
All in all, Sublevel Zero may not be a masterpiece, but I enjoyed every minute I spent with it, and considering how fair the pricing is, I can recommend it wholeheartedly to fans of 6DOF games.