I know it seems like the green glass door is very selective about what may pass through, but if you know the rule, you'll see that tons of things are allowed!
Well, maybe not tons of things...
Answer Checker:
Hints: The "green glass door" is not an original invention of Ryan's EnigMarch. It's something you can google. The first letters of each answer don't give you the answer to the puzzle! They give you a CLUE to the answer of the puzzle.