Though the player fired a rocket across the starting location of Introduction, the lightning is being fired at 90 degrees, down the Hard corridor, due to the player changing their orientation.
ROCKETS WITH GUIDED LIGHTNING is a modification for Quake made by Remco Stoffer. This allows rocket projectiles from a Rocket Launcher to fire lightning that is entirely guided by the player. Note that this means the Rocket Launcher will now no longer cause explosions, the rocket is only used to propel the projectile forward.
This can be relatively useful at attacking opponents around corners and will not alert Monsters to the player's presence. However, the lightning will only start appearing after 0.5 seconds from the time fired, meaning that the Rocket Launcher cannot be used for close combat.
Furthermore, the requirement to aim the lightning means that the player must always be guiding it to an opponent by moving in the direction they wish for the lightning to fire. This can be difficult in Deathmatch, where the player doesn't have the time to stand around and guide a projectile to their opponent.