Cool concept with adorable art.
My crystal's health went into the negatives at the end, but I guess you already know that this happens at this point :)
As far as improvements go, maybe you could make it so the crystal always stays a minimum distance away from the and holes. I had ants spawn literally on top of it with now way for me to react at some point. Or maybe one of the elemental's abilities can be used to prevent that? If so, I haven't figured it out yet.
Anyway, it's a good game, especially considering the time frame, with no major bugs. Nice work!