aha, you're right. My personal score is 7 points. I think there are 2 relevant problems, it cannot see what will be the next block, so it is easy in a short time to haven't space. (Precisely, a block is created when no other block can move), Then, all blocks have 25% of being ( I assume because don't check if or what Math.Random of libgdx use a probability distribution). But this is unfair because only a lava block can destroy a block and a water block can destroy only a lava block (but destroy her self).
I think it must be used a distribution probability that is dependent by time (and/or score), so at the start less no destruction block... at the end lot of these