Oh gosh, the downloads are huge.

I downloaded as many of the things listed here (http://ethicalgames.wordpress.com/2013/06/25/unity-asset-store-100-free-assets-in-my-new-unity-asset-store-guide/) as I could, then used them to make something interesting to explore. I don't know what happened to the jumping, but it's good.

Windows and OS X builds in the same Zip file!

Dig down... but make very sure you can still climb back out to the surface again!

Arrow keys - move
Z - jump
X - dig down, left or right