The AI in modern games is algorithmic - a programmer writes a very specific set of instructions on how to identify and react to specific game situations. For example, a programmer might code in something like "if the area had enemy activity and we haven't scouted it for a minute - make scouting it a high priority".

In this case - the author built something that's closer to being a "generic bot". Basically, you take this AI, wire in a bunch of inputs (position of legs, arms, maybe obstacles) and take back from it a bunch of outputs (key presses). Then AI just tries to figure out how are inputs related to outputs by observing said inputs and trying to constantly improve. So it starts with random keypresses, but then starts to notice and remember patterns.