I'd love to get some more testers, as I'm keen to gather impressions and make refinements - I'll be posting some sample video this weekend.
In the meantime, here's an overview of the gameplay so far:
Picture Dig Dug, but with gravity. In most levels, goal is to collect a burried prize, then return to the surface. You can run, jump, dig straight down, or dig sideways. In order to complete a stage, you need to make sure that you leave an escape route. For example, if you just dig straight down to the bottom of the screen you'll be stuck at the bottom of a deep hole with no way to climb/jump back out.
As a wrinkle, the game features boulders which block your path. You can destroy them from above (with jackhammer) or push them from the sides.
Monsters include bats, goblins, and fireball spewing devils. All crushable with boulders, of course.
Levels are split up into separate puzzly and arcadey sets.
The latest beta includes a new "Creative Mode" which lets you set up and try your own levels.