Heya! If the player moves a gray block into an any fire the game crashes, which isn't good.
Regarding other feedback, for now there isn't much content to analyze, but the mechanics look interesting for now and the interactions between the different objects will be interesting to use. For example, it'd be interesting to see what would happen if a flame interacted with the lava pillar/river.
Good luck with the rest of the time for the jam!