Or rather, which kind of shift is the closest in shape to a power-up?
Let me explain. I wanted a house with a ghost in it to talk after the player got the ghost eye, and because using signs in an empty house looks weird, I needed to use flag warps for it. At first I used a square shift because I wanted to make extra sure the player triggered it when they got the ghost eye, but later I realized that it worked a little too well, and it was possible to trigger the shift without getting the eye. So now I'm using a circle shift. However, I'm not sure it's impossible to trigger one without the other here, either. So what kind of shift would work best here?