I need more! I need to go deeper!
First of all the art and music were fantastic and I had such a great vibe and time throughout the demo. I love games like this and I instantly want more.
The opening scene was amazing and really funny with the "You are a rock. Move with WASD. Rocks cannot move" really got me.
There was a little issue where I could already throw pickaxes at the start before I even had arms and as you mentioned in your description a little cache/lag issue but that didn't' stop me. I also quickly closed the end of demo popup and read the info.
I kept digging until I think I found the bottom where it was just an unbreakable blueish wall.
I really enjoyed this and my only complaint is that it was too short. Give me moreeeee!