Level 16 Press the buttons on the door to spell "KEY".
100 Doors 2 Level 17 Walkthrough:
Level 17 Tilt your phone and make the sphere stay on the button until the bar fills up.
100 Doors 2 Level 18 Walkthrough:
Level 18 Adjust the height of the weights to match how heavy they are. First tap them so they're all even at the top. Tap "4" 1 time, "8" 2 times, "16" 3 times, "32" 4 times.
100 Doors 2 Level 19 Walkthrough:
Level 19 Tap each fly and see how many line segments they make to get the code = 4643
100 Doors 2 Level 20 Walkthrough:
Level 20 Count the number of tires on each object from smallest to largest to get the code = 0422.