random left-handed progress(?)

Here's another thing I never expected to be so challenging to do left-handed: swirling water in a cup.

There's a powdered drink mix that I like, and the best way I've found to get it to dissolve easily is to fill the cup halfway, put in the mix and swirl it around until it all sinks, then add the rest of the water and shake it up.

Lefty Shaking: easy!

Lefty Swirling: hard!

But WHY?!?