Here is the full list of all 32 Gravity Den achievements.
Collect 10 stars!
Die a hundred times!
Complete level using only gravity shift!
Die a ten times!
Die once!
Scare away a raven!
Open the About window
Collect all stars in the hardcore levels!!!
Collect all stars in the normal levels!!!
Collect all stars in the hardcore zone #1!
Collect all stars in the hardcore zone #2!
Collect all stars in the hardcore zone #3!
Collect all stars in the hardcore zone #4!
Collect all stars in the hardcore zone #5!
Complete all hardcore levels!!!
Complete all normal levels!!!
Complete all levels in Hardcore Zone #1!
Complete all levels in Hardcore Zone #2!
Complete all levels in Hardcore Zone #3!
Complete all levels in Hardcore Zone #4!
Complete all levels in Hardcore Zone #5!
Complete hardcore level using only gravity shift!
Complete 5 hardcore levels using only gravity shift!
Complete 10 hardcore levels using only gravity shift!
Complete 10 levels using only gravity shift!
Complete 20 levels using only gravity shift!
Scare away 250 crows!
Scare away 1000 crows!
Die a thousand times!
Die ten thousand times!
Collect 50 stars
Collect 100 stars!!!