Level 51 Count the number of planks between the black lines at the top. Also the number in the floor. Code = 1625. Special thanks to Kristin for this answer! :)
100 Doors 2 Level 52 Walkthrough:
Level 52 Play minesweeper. Tap the following safe blocks: Row 1 = All Row 2 = 3rd Row 3 = 1st 3rd 4th Row 4 = All Row 5 = 1st 3rd
100 Doors 2 Level 53 Walkthrough:
Level 53 Tap the bottom left floor to find a hidden panel. Pick up the triangle and place it on top of the stone triangle images. It'll show you the correct order to put the triangles in. Tap the triangles to switch the order.
100 Doors 2 Level 54 Walkthrough:
Level 54 Make the blue line match up with the red line. Tap the left knob 6 times and the right knob 5 times.
100 Doors 2 Level 55 Walkthrough:
Level 55 Pick up the lightsaber and put it into the slot in the wall on the right. Take it again and use it on the blue crystal to cut a piece. Pick up the blue crystal and place it in the slot in the wall.