An interesting little puzzle game! Having to melt and freeze your way through levels was a neat idea, and turning it into a puzzle game really worked for it, I think. The levels were well designed, and the difficulty was just right too - I didn't just breeze through each level, but I wasn't stuck for ages either. The mechanics were introduced nicely as well, although sometimes it was unclear about certain things - I didn't realise I could heat up the water twice!
The graphics were nice, and having things colour-coded red and blue was a good way to visually distinguish things. I liked the cave environment as well, it was a good place for the setting of the game! The tiles did flicker a little bit, though, which was kind of distracting - when it happens to me, I usually just make the tile size 1.01 or something, to make it less visible. The lava (was it lava?) looked a bit odd too, with the colours of it, but it was nothing too bad or distracting.
It was a nice experience, playing this game, and it has a lot of ways to go in future - nice work!