Straferunning is a tactic which has developed within the first person shooter genre. Roughly, it allows the player to run faster through levels by moving forwards and sidewards at the same time. In this way you walk in two directions at the same time. The game will combine these actions and will make you run roughly 40 percent faster.
Based on the pythagorean theorem, a player starting from the vertex of CB who moves simultaneously right and forward would be seen moving a greater distance (the length of side C), as opposed to a player who chose a straight path from vertex AB and would travel a distance the length of side A. Both players would arrive at the same point, however the first player pays nothing for the sideways movement.
Since straferunning became popular and it is widely regarded as Metagaming, many games have thought up special rules which would cause the straferunning player to become actually slower than normal running.
