Here is the full list of all 20 GNOG achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Leave no trace
Daydream at the blackboard
Please don't bother the amphibians
Keep the kitchen clean
Test the astronaut for space sickness
Watch what you eat
Finish the game
Complete LAB-O
Complete HOM-3
Unlock every level
Complete CANDY
Complete EATER
Complete LOG
Leave no worm behind
Complete VORT-X
Complete PURP-L
Experiment in the studio
Complete SUB-01
Discover what lurks below
Complete FRG-Y