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.
Rescue 100 sea critters
Collect all the timed orbs
Rescue Cactus, Holly, Lemon, and Coral from Assault Android Cactus
Rescue the Shopkeeper from Crypt of the Necrodancer
Rescue Snakebird from Snakebird
Rescue Guac from Burrito Galaxy
Rescue Fish from Nuclear Throne
Find a hidden level
Beat The Fall of Gravity
Beat the game in under 60 minutes!
Beat a level with Red
Unlock the final zone
Die 500 times
Beat a level with Green
Rescue 50 sea critters
Beat a level with Blue
Die 100 times
Beat a level with Purple
Unlock a Containment Level
Beat the Octosphere
101% the game
Rescue all the sea critters
Die 2500 times