|The key and key door in game.|
The Key Door is a three tiles long, blue, fine barrier with a red light in the middle. If the player attempts to open it without a Key, the red light will blink and the door will play an "invalid" noise. If the player opens it, the light turns green and the top and bottom segments make the way to the center, to which the door disappears and clears the path.
A Key Door is solid and blocks the path. Due to their size, the vertical ones can be cleared with a normal jump from the player. As of version 1.3.6, it is not possible to have a Key linked to a Key Door, meaning any Keys can open any doors. It opens when the player touches it with at least one Key. Upon collecting a Checkpoint, any previously opened Key Doors will remain open after death or restart in the latest checkpoint.
Horizontal variants work the same as the vertical, aside from their position.
- The Key Door, along with Keys, were the final items announced for 1.2 before the release date was revealed.
- The Key Doors behave very similarly to the Key Doors featured in Zelda II: The Adventure of Link.
- Originally, the Key, along with the Key Door, used the same design as the ones from Make a Good Mega Man Level 2. However, it was changed due to the design not fitting the Mega Man universe.