Nyxen lives in a world where even his own shadow is fighting against him. Your shadow learns from you and follows your movement patterens. Your movements in the past are his in the present. Understand his fighting logic and you will be able to defeat him. 

Your shadow either mimics your moves exactly or comes up with a surprise attack. Think well of your attack sequesnce as some hits are stronger than others and if your shadow attacks you with the same hit you are doing then no one gets damaged.

Controls:

ASWD or Arrows for Movement

Space Bar for Jumping

X for Kicking

Z for Punshing

More controls that gets unlocked with advancing levels:

Combine X or Z with Jump  for an even powerful hit

F for Special Attack