■ 🕑 11. optical illusions
             /\   \        Moebius Triangle
            /  \   \
           /    \   \
          /      \   \
         /   /\   \   \
        /   /  \   \   \
       /   /    \   \   \
      /   /    / \   \   \
     /   /    /   \   \   \
    /   /    /---------'   \
   /   /    /_______________\
   \  /                     /
    \/_____________________/   mn
   
       _____________________
      /  __________________()
     /  /|_________________ 
    /  /_/________________()
   /______________________
   |_____________________()   mn