Yeah, I threw that angled "Start" button into the intro just to make the player click in the window so that wouldn't happen. Sometimes it feels like WebGL builds have more quirks than a country fence! XD
I'm most likely going to create collapsible panels in future builds, and this should create room to have a clickable Start button and other such things. I agree, not every player is going to prefer hotkeys over a good reliable button, not least because you can't forget a button the way you can forget a hotkey!
I more or less ran out of time (and energy) before I could add sfx to the parts, but it's nice to know I'm on the right track. And yes, I'm a big fan of diagetic UI (interactive main menu) in general. Thanks for your feedback!