After four years, I've again attempted to make the smallest possible project. And when I download it (due to that darn "agent" (user agent) value, it's 473 bytes. I'm not sure I can link you to it because of any current or future rules, but I've been able to get an SB3 down to 245 bytes. Not even a quarter of a kilobyte! Impressive, considering Scratch projects are a lot less efficient than what could've been.
