Thanks! I'm glad that you're enjoying the game! We are very open to feedback!
The idea you came up with is very similar to what we had planned, though just ran out of time to implement it. We were going to do something very similar to that concept only it was going to be a strength, weakness thing with the elementals. Fire rocks, ice rocks, and charged rocks. Fire would be weaker to earth, earth weaker to ice, and ice to fire. That whole triangular system. I like the idea of having some types be AOE as well, that would be a cool system to add as well.
We did build for WebGL, though the downside to that is our Voxel system that we created to dynamically generate the levels took really long to load each level, and it really hurts the smoothness of level transition, since WebGL doesn't take advantage of multi-threading nor burst. We did try to get a good WebGL build and it does run that way, just really takes you out of the immersion of the game when you have to wait a full minute for the next level to generate and load.