A group of Tokyo University researchers from the Virtual Reality Society of Japan recently developed a VR experience (we’ll call it a game) in which the user can dislodge a “Holy Sword” from an altar in real life (embellished in virtual reality, of course). However, no amount of physical power can make the sword budge – the player needs to use the power of their concentration. Unsurprisingly, learning of this fun experiment, users were quick to make a connection with the divine Master Sword featured in the Legend of Zelda series.

A paper titled “The Legend of the Holy Sword – Proof of Concentration” published in September 2023 reports on an experimental VR game that is played by consciously raising your level of concentration. The apparatus includes a “Holy Sword,” consisting of a hilt, crossguard and blade, and an “altar” (pedestal) that the sword is driven into. The blade of the sword is connected to a motor via cable, both located under the pedestal, and motor torque makes it so that the sword cannot be pulled out by physical force.

The player wears a VR HMD (head-mounted display), a brain activity measuring device and headphones. The HMD obtains data on the player’s line of sight and combines it with brain wave data, measuring concentration. The player’s goal is to raise their level of concentration to a certain point, and if successful in doing so, the concentration fed back into the apparatus will cause the motor attached to the blade to loosen the cable, allowing for the Holy Sword to be dislodged from the altar.

The project also seems to have taken into account player immersion – a ToF depth sensor attached to the sword makes sure that the coordinates of the sword in real life and in virtual space are aligned, and the hilt has a vibration motor built into it that sends vibrations to the player’s hands when gripping the sword. The intensity of the stimulation seems to change depending on the player’s level of concentration too. To top things off, the crossguard contains fans that blow a triumphal gust of wind into the player when the sword is successfully pulled out.

It seems that the goal of the project is allowing the player to experience the sensation of consciously raising their concentration level, and this is achieved through the real-time concentration feedback system.