You're only targeting old 1990s GUI users there, though.
If you wanted to also help silghtly more modern users who are used to discoverable-UI conventions from mobile apps, you would have it so shaking your device brings up some form of chat bot, which would suggest asking it how to quit Vim.
If you wanted to also help slightly more modern users who are used to CUA conventions from GUIs, you would have the [F1] key bring up some form of help screen, which said something like "Get out of Vim: Use :qa!" at the top.