29. Dance Floor?

The floor of this room is covered in what appear to be milky white quartz flagstones which glow a warm white color from within. The room appears otherwise empty. The room is in fact empty. Some of the tiles glow slightly bluer than the others. Any character might notice this on a 1 on 1d6 with a casual look, or 1-2 on 1d6 if carefully examining them; both elves and dwarves do better, 1-2 on a casual look and 1-5 when actively studying them. These "bluer" tiles form a dotted line from the entrance to the secret door, and the only way to open the secret door is to cross the room while stepping only on the bluer tiles.