Here is the full list of all 18 Mindset achievements.
Finish Training
Complete ten levels
Complete twenty-five levels
Complete fifty levels
Complete all levels
Find any set
Find a hard set
Find fifty very easy sets
Find one hundred easy sets
Find one hundred fifty medium sets
Find two hundred hard sets
Finish ten random levels
Complete a hard random level
Use every symbol in the game at least once
Find a hard set first on a board
Complete two packs
Complete four packs
Complete six packs