The article talks about “If I want my friend to fight in the arena” and gives “One way path, with the drop down” as one possible solution. I absolutely abhor arena fights, especially with auto-closing doors or a drop down. I would always try to trigger as few enemies as possible, and would always retreat to fight them safely if possible. Why would you design levels which makes it impossible to play in this style, if some people prefer it? Why would you design a level to force a specific play style, even though they might not enjoy it?