IThis is the first time i've played the game since briefly playing the gameboy and ps2 version and now i'm kinda confused on something. I've gone through about five hours of the game and have came into contact with a Key door that requires a card I have not yet came into contact yet. It's a card with something that looks like a door and has light coming out of it. I'd really like to know if I should go back and do whatever it is you do with that card before I continue going through the floors.