A very fun concept for a game I think. The game takes a moment to fully understand but once I started to get it I was able to beat the first few difficulties.
The hard difficulty was one that was honestly really challenging as I actually had to figure out how heat transferred (Which is unfortunately not the clearest. might work better with some indicator on where heat flows). Even with that though I managed to softlock myself multiple times and even find a pretty game breaking bug where I just placed a fuel rod in the delete button and broke it entirely.
This is just a jam game and a prototype so it makes sense but the music was quite an annoyance at times (thank you for the mute button).
overall I think it could make for a great little puzzle game especially with a few more elements introduced to spice up gameplay.