"The game with no aim"

But it does have a name:  Sandspiel.

At the link you can read the "info" if you want, or just start clicking.  Choose a dot to select the size of the elements you want to insert.  Then click on the element and then on the drawing space.  There is a "freeze-frame" in the upper left if the lava or exploding gas get out of hand.

With a tip of the blogging hat to Miss Cellania, who always finds and posts the best flash games at Neatorama.