Early in hq3_1, the path splits in two - one takes you up a long flight of stairs then back down through a room of spikes, the other leads you to a "train of electricity" you need to avoid while activating boxes.
The second path (train of electricity) arrives in that room through an exit that is above the exit of the first path: https://pasteboard.co/Jmytllc.png (second exit seen from first exit)
It is possible to drop from that upper exit back into the lower exit, reaching the room of spikes from the other end. The trap will sort of play in reverse but will not complete. Yet, as the trap activates, the exit (by which we came through) gets closed, and so we end up being stuck in that spike room with no way out.
I guess that to prevent this, when we go into a particular path, the exit of the path we did not choose should close, to prevent us from going back into that other path through it.
Early in hq3_1, the path splits in two - one takes you up a long flight of stairs then back down through a room of spikes, the other leads you to a "train of electricity" you need to avoid while activating boxes.
Both paths then end up in the same narrow room: https://pasteboard.co/JmytA8k.png
The second path (train of electricity) arrives in that room through an exit that is above the exit of the first path: https://pasteboard.co/Jmytllc.png (second exit seen from first exit)
It is possible to drop from that upper exit back into the lower exit, reaching the room of spikes from the other end. The trap will sort of play in reverse but will not complete. Yet, as the trap activates, the exit (by which we came through) gets closed, and so we end up being stuck in that spike room with no way out.
I guess that to prevent this, when we go into a particular path, the exit of the path we did not choose should close, to prevent us from going back into that other path through it.