In certain missions fights will have "rules" - additional conditions that affect the gameplay.
Here is a list of rules you can meet:

  • Fight in the dark
  • Inverted controls
  • Score victory
  • Opponent is in Shadow Form
  • Opponent regenerates
  • Health drops over time
  • Passing bleeding effect
  • Win on timeout
  • Fists only
  • Kicks only
  • Unarmed fight
  • Restore health with hits
  • Enemy restores health with hits
  • Opponent is invisible
  • No jumps
  • Head hits only
  • Stacking poison effect