Really cool mechanic and nice progression curve!
One thing that bothered me, after the lava-cubes fell, i had to click on each line to fill it up to the top again, but since i can only see the first block, couldn't that be done automatically?
Also, i would maybe make the level a bit smaller, it can be a bit overwhelming trying to take everything into account.
But on the whole, really great entry, could probably work well on mobile if you flesh it out!