In ShurikenVR, the levels are meant to be played in a specific area, as the environment outside of that area is not properly populated, as seen below.
So to prevent the player from leaving the designated play area, boundaries are set at the edges of it. This is done by placing a box collider which will only collide with player and the teleportation kunai (using the collision matrix in Physics settings). I’ve also added a fancy shader that will only appear (locally) when the player gets close or is hit by the teleportation kunai.