Question: how to write the upside down exclamation point?
Answer: On the macOS platform (or when using the "US International"/us-intl keyboard layout on Windows and Linux), ⟨¿⟩ and ⟨¡⟩ can be entered by pressing Alt / ⌥ Option + 1 and ⇧ Shift + Alt / ⌥ Option + / respectively.