Introduced in Black 2 & White 2, the key system is a feature that allowed you to link up with another copy of the opposite version locally via infrared to obtain a key that unlocked new features in your game. Among the features unlocked include difficulty modes, the ability to switch between Black City and White Forest, and also catching Regice or Registeel in the opposite version.
What did you think of this feature?
Did you think the inclusion of difficulty modes was worth it or not?
Were you sad that the difficulty modes never came back in following games?
Did you ever catch Regice or Registeel using the keys?