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The pulse is an unknown shockwave that occurs about three quarters into the game. The only warning given before the wave blasts across the screen is a distant flash of light and a loud noise before it hits. The pulse occurs approximately every five seconds. Most objects to the left and in front of the protagonist will protect him from the pulse; If the pulse hits the protagonist, their body parts will dismember into chunks and fly towards the screen, resulting in instant death.
The facility/laboratory that contains the pulse (sector 2) is located in a massive subterranean cavern, large enough to have its own shoreline and beach. The facility's entrance and interior before the pulse contain mining equipment and stations, along with remote bodies that have been left there, suggesting that the vast atrium which holds the pulse was mined out.
The gate to the atrium is only able to be accessed if the weight of twenty individuals is placed on a pressure-sensitive plate. The protagonist completes this by controlling the various mining workers around the area to follow him.
The atrium's initial area contains sandbags and still-functioning construction equipment as the protagonist progresses, alongside mechanically manipulated blast shields, of which, several seismometers can be seen nearby.
According to many theories, the pulse was designed as a failed sonic-based/seismic weapon. This theory is supported by the presence of multiple bound crash test dummies in chairs, and a man-portable blast shield that is able to be used for deliberate protection against the pulse. Also, the fact that the pulse can hurl objects, such as barrels or boxes, at speeds that can damage concrete indicates that the pulse is most likely a mass destructive weapon.
Another possible theory is that the pulse was used for mining rock beds like the one seen before reaching the atrium. However, the pulse does not indicate any ability to break apart rock or metal, making this theory only plausible at best.
- The music during the shockwave portion of the game is synced directly with the coming and going of the wave. During the second half, the music changes from heavy wind-blast type sounds to an electronic pulse.