Here is the full list of all 27 Squarism achievements.
Finish 20 levels
Sticked
Complete level with that huge 4x4 square
Use restart 10 times
Finish 10 levels
Fail level 3 times
Make wrong shape
Complete tutorial levels
Complete level after 5 restarts
Use restart
Complete first level
Finish 30 levels
Finish 40 levels
Finish 50 levels
Finish 60 levels
Solve last level
Solve everything
Destroy your only movable shape
Spend 5 minutes solving single level
Spend 20 minutes solving single level
Spend 3 minutes in level selection menu
Breached
Hivemind
Opened
Guided
Sacrificed
Spend 5 wonderful minutes in credits menu