I really liked this. I couldn't quite get past level 3. I liked that the rock got unstable in response to crashing but considering that the rock also becomes unstable after a few seconds of gameplay, I found it tricky to get to the goal in level 3 because I was trying to race to get to the objective. I don't think it's impossible as I did get close a few times. But if that wall in the middle was just a little shorter, it might have made it easier to navigate. I think this one of those things where the rock's instability could be in proportion to the difficulty of the level. So for the first level, I think it's fine if the rock becomes unstable after a few seconds but in levels with more hazards, it might be nice to increase the time of the rock's instability so that people don't feel they have to risk crashing into walls in their haste to get to the objective.
I did really like that the rock would explode based on the force in which it would hit the wall. I noticed that if it lightly brushed against the wall, it would become unstable but would explode if I was rushing and got flung into the wall. And the rock itself was nicely done. I liked the glowing effect as it got more unstable.