Hint
As you work your way through the puzzles keep track of the letters that appear on the screen after you solve the puzzle. You will need them later. Several of the puzzles contain clues that seem to make no sense at all and are just random letters. Try saying the letters out loud to determine if they can become a word. For instance, if the clue is "PL", out loud this could become "PEEL" or "PEAL".
Spoiler for last elevators puzzle
Warning: the last note can potentially spoil gameplay! The last set of elevators can be traversed using one single key. Press the far right key and all the others will align for the 3 to cross all the way from left to right immediately.
Spoiler for Inside Track puzzle
Warning: reading this hint might spoil gameplay! In each of the puzzles for the Inside Track the number of the puzzle is spelled downward across the other words. You can locate where to put the number by inserting letters in the squares. When the square turns a different colour you know that is where you should be able to spell the corresponding number.