Here is the full list of all 24 Hazel Sky achievements.
Complete the first machine.
Complete the second machine.
Complete the third machine.
Find the secret ending.
Escape from the Gideon.
Collect all badges.
Collect all keys.
Inspect all books.
Play all songs.
Stay underwater for a long time.
Feed the cow 5 times.
Find Shanes’s Mom Letter.
Collect one badge.
Collect one key.
Inspect a book.
You can't escape!
Play a song.
Inspect 8 objects.
Inspect 16 objects.
Run for a long time.
Fire a cannonball in the ocean.
Go to the watchtower.
Find the moon pamphlet.
Become an engineer...?