How do I Open the Red-Locked Doors?
If you climb to the very top of Dustforce's hub world, you find a row of locked doors, and a scientist with the following message:
I wouldn't go in there if I were you.
How do I open these doors? I don't want to know what's behind them, so please don't post it in your answer.
Solution 1:
You need to get a SS on a gold door level to get a red key.
An SS on a silver door gets you a gold key.
Spoiler withheld by request, but iirc there are 16 red door locks here ;)