I like the concept idea. I'd like to see later levels. There are a few things about the lava which bother me. First of all, as its random, you can't really plan for it. Maybe it should fire left or right in a pattern, and it might be good to have some sort of tell to give you a second or two warning.
Also, the lava interacted with itself and other items. In one instance a lava block sat on a platform that I had no chance of avoiding, and on another level, the lava knocked away one of the blue blocks.
Simple graphics are fine but create a nice colour palette.