I named it after a worm because it was a snake-like with digging :) Just like snakebird is snake-like game where birds are involved...
As you and more people noted, the game misses the animations of 1 pixel resolution (the game has only 4x4 blocks) to show when the soil collapse and when the worm falls, but I really had not time to implement them with a small son to take care of :-p
More things I would like to add are sound (of course), falling bonuses to create more complex puzzles and a better font.
The current rules are: first the worm move, then the soil collapse, then the worm falls (all in an instant)
And the soil collapsing rule is that soil that is connected to rocks (the white ones) by a 4 connectivity won't fall.
Thanks for the review! :)