I'm developing a simulator where the player has a dual life. In the front of the shop, they are decorating and selling shoes to customers legally. In the back basement, they are ordering raw materials and manufacturing illegal replica sneakers, trying not to get caught by police raids.
I'm struggling with the UI and notification systems. When the player is focused on serving a customer in the front, how do I elegantly alert them that a machine broke in the back or the cops are approaching, without it feeling annoying or overwhelming? How do games like Dave the Diver or Moonlighter handle this split-focus so well?