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