It shows where you can click to interact with the environment. I made it work in a kind of hacky way, so Ren'Py stutters a bit to show the visual effects. The next step is to refactor and optimize this code a bit, so I can make it more versatile and responsive for future updates.
I need a proper name for this feature. I'm calling it an "exclamation mark" in code, but it won't hold much longer, as I could make it show other symbols for different interactions.