Very fun game, probably the most enjoyable demo I tried so far. It plays like a finished game, I only have some minor issues.
The weapon recharge bar feels kind of in your face, looked a little ugly to me. Can't it be the same way as the rock recharge? Or maybe if that's not enough it could have a visual or an audio cue. The menus work well but are a little tedious to go through, especially when I had a lot of items. I think it may be because its very small. I didn't check for any UI scaling options but the default felt tiny at least.
The weapons feel nice to use, I like the rocks especially because of headshots and bouncing. The spells are also very fun to use. Only the RMB attack felt a little underwhelming, its too similar to the LMB but very slow.
Overall, great job. Its a very solid base, just needs some more content.