Hi, loved the general aesthetic and design of the game. I found it a bit hard at first to work out what each block type did, but once I did I really enjoyed it.
However, I did run into a bug where I tried removing a crystal and it completely crashed the game.
I also struggled a bit to see how it relates to the theme "Multi-use" or indeed "Turn up the Heat". *
Overall, I think its one of the best games in the jam, it is just unfortunately too buggy at the moment.
* Just as an fyi, I'm being more critical in this comment because I noticed you're a more experienced dev and I believe your game really has potential.