I’ve added doors.
They open! They close!
Is there anything they can’t do?
The doors (and buttons) are implemented with character (tile) graphics rather than sprites. So when they animate, they are changing the map layout. One nice side effect of this is that closed doors act as walls for all intents and purposes. I don’t need to implement any door-specific collision routines for them as they automatically block the player and assorted bad dudes, and allow the player to use them for wall-running and wall-jumping.