In total there are 5 levels with increasing complexity:
Level 1 : 3x3 puzzle
Level 2 : 4x4 picture puzzle
Level 3 : 4x4 without thumbnail picture puzzle
Level 4 : 4x4 with time limit picture puzzle
Level 5 : 4x4 with time and maximum moves limit picture puzzle
Tip : You can swipe a piece from a right most corner to an empty left most corner.