Here is the full list of all 50 Merri Puzzle achievements.
Make a ball
Bounce things off of more things!
Use the wobbly triangle
Touch two triangles in puzzle mod
Check point found
Encounter lava
Reach a locked room
Reach a room with gravity controls
Use the red square of awesomeness
Encounter vanishing blocks
Encounter exploding blocks
Encounter green diffuser blocks
Break some breakable blocks
Encounter yellow blocks
Beat easy mode
Beat Hard Mode
Encounter Invisible Walls
Reach Expert Mode
Beat Expert Mode
Multiple Objects in One Room
Use Green Blocks To Break Red Blocks
Reach Check Point 2
Reach Check Point 3
Reach Check Point 4
Reach Check Point 5
Reach Check Point 6
Reach Check Point 7
Reach Check Point 8
Reach Check Point 9
Reach Check Point 10
Reach Check Point 11
Reach Check Point 12
Reach Check Point 13
Reach Check Point 14
Reach Hard Mode Check Point 2
Reach Hard Mode Check Point 3
Reach Expert Mode Check Point 1
Reach Expert Mode Check Point 2
Reach Expert Mode Check Point 3
Reach Expert Mode Check Point 4
Reach Expert Mode Check Point 5
Reach Expert Mode Check Point 6
Reach Hard Mode Check Point 1
Encounter gaps in a level
Encounter a pit
Encounter a level with more than one solution
Encounter a level with two exits
This really is the pits!
MORE PITS!
Encounter a peg based level