Wierd blue/gray screen with black 2D ball

Wierdest thing just happened on my Macbook Pro used with a BenQ 32" monitor. I was in Safari and pressed some buttons not sure what they were and a dark blue/gray screen showed up with a medium sized black 2D ball that bounced between the four walls. Quick scan with Antivirus says clear.

I don't remember the Exact time it happened now but it was between 18:45 and 19:10. Is there a way to submit diagnostics to Apple so that they can check what happened?

Very mysterious I've never seen anything like it in my 10 years of mac usage.

Thanks!