Brilliant little puzzle game, that provided hours of fun. Some later puzzles are quite challenging too.
I found a little bug in level 88. After eating the clam and digging through the dirt on the second lowest row left to the stairs, the column left to Millie collapses:
The column is still there, even though it seems to disappear. You must exit and re-enter the level to get the graphics looking proper again.
Not a huge issue though, as this is a stupid move anyway. :) But thought it is worth mentioning, in case it can happen in some other levels too.