Here is the full list of all 8 Curvatron achievements.
Finish every level in the Adventure mode
Get 4000 points in Evergrowing mode
Get 30 points in Classic mode without collecting any shrink powerups
Finish a community level
Have two players kiss in Multiplayer mode
Take a bite out of yourself
Get 30 points in Classic mode, collecting all shrink powerups
Finish every Hardcore level