Here is the full list of all 16 Plith achievements.
Finish the first puzzle.
Complete the first world.
Complete the second world.
Complete the third world.
Complete the fourth world.
Complete the fifth world.
Use a small gear first time.
Use a middle gear first time.
Use a big gear first time.
Place 100 gears.
Place 500 gears.
Destroy a gear with dynamite first time.
Destroy 10 gears.
Destroy 50 gears.
Complete the game without losing in any level.
Start a new game and complete it without saving/closing the game.