>>717928917
There is, but it's extremely subtle, and that image ocbsures it.
This is a lighted room, with Firefleas that when killed make the room darker and darker until it's pitch black. Lighted rooms glow. The secret passage is actually illuminated by this glowing effect, but only very briefly on the brightest frames. If you kill even one of firefleas, the room becomes too dark to see the passage. Luckily the firefleas aren't in your path to the top of the room.
Pic related. You can see the passage.