Here is the full list of all 23 Airscape - The Fall of Gravity achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Die 2500 times
101% the game
Beat the Octosphere
Rescue all the sea critters
Beat The Fall of Gravity
Beat the game in under 60 minutes!
Beat a level with Red
Unlock the final zone
Rescue Cactus, Holly, Lemon, and Coral from Assault Android Cactus
Rescue 100 sea critters
Die 500 times
Beat a level with Green
Rescue the Shopkeeper from Crypt of the Necrodancer
Rescue Snakebird from Snakebird
Collect all the timed orbs
Rescue 50 sea critters
Rescue Guac from Burrito Galaxy
Beat a level with Blue
Die 100 times
Rescue Fish from Nuclear Throne
Find a hidden level
Beat a level with Purple
Unlock a Containment Level