app menu is somewhat hard to notice
I upgraded to 3.30.0.1 and almost reopened #13 (closed) because it took me a while to notice the little icon in the top left of the app.
The convention suggested by https://wiki.gnome.org/Design/Whiteboards/AppMenuMigration is to use a 3-line "hamburger" ☰ or 3-dot ⋮ menu in the top right of the app.
But other "simple" GNOME games just include a lot of those buttons in the headerbar. Maybe all but About could just be a button. Quit is no longer needed since people should be able to use the X to exit the app (or a few other ways).