How did that person do this

So, I was playing an ultrabullet game, and somehow my opponent was both spectating AND playing against me at quick speed... I mean, how is that possible?! I cannot spectate my own games, unless I open another tab and it's in a simul, but otherwise, IDK how the person did this.

@ultramuddish
First, BEFORE playing, open a new tab and copy your game.
Then open the first tab and play your game.

no no, he's actually the Flash, he likes to spectate his own games once in a while. Nothing special.