I'm sorry, but I'm not grasping the concept or purpose of this game. 1 Star for effort.

Well, obviously the sand is not really sand, but more like sand blocks and the lava is lava blocks, too. But for just having three different elements, it's quite entertaining, even if it's just for a few minutes. If I was a bit more creative it could have been for longer, and I think the fun would grow exponentially, dependent on how many more elements you'll add.

There's not much to do. Lava burns the sand and stones can overlap each other. That's the only interaction you're going to find in this game. The game needs a lot more.