Cavern Kings, as it's called, is an infinite action-platformer for PC that gets harder the longer you play. It's a very leaderboardsy game, and it's actually quite a bit deeper than it looks.
The game works like this: you start out on ground level, where you pick up a digging tool, be that a shovel, a jackhammer, or this really cool hydraulic fist. Then, you dig your way down to the first level of the randomised, infinite dungeon, where you can pick up your first weapon.
At that point, the game becomes this delicate balancing act where you need to keep track of several things at once: enemies, treasure, navigation, your health bar, and, if you stay long enough, the descending ceiling. As you're constantly attacked by monsters, you need to jump around the stage, collecting gold and beating back the horde, and decide how long to stay before moving to the level below. It's quite frantic.
Apart from an infinite dungeon, Cavern Kings also has an infinitely stacking powerup system, which means you get to keep and use every powerup you get. This could lead to some pretty interesting combinations, especially since there's 50 powerups in total. Besides that, there's four player characters and four bosses to give the game even more replayability. Of course, as it usually is with games like these, there's also permadeath. When you eventually die, the game's leaderboardsy aspect comes into play: you get separate scores for depth (in feet), kill count, character level, and money.
The developer's running a Kickstarter campaign for the game, but it's already almost halfway funded -- no wonder, since the goal is just $US2500, and the game looks great, to boot -- so it's probably a safe bet that Cavern Kings will be completed. It's set to arrive in December. Until then, give the free public beta version a try.