I was keen to understand how it works and what this "flow" thing is, as the technical premise is really quite interesting. So I click on the video... and start hearing the xylophone... and say "uh oh".

Folks, I have good feelings about good tools, but I don't get them from watching videos of people talking about how they get good feelings from their tools. The promotional video has obvious high production values but lacks any description of what "flow" is/does. It is the 2010s hipster equivalent of zombo.com.

Tell me what it is, what it compares to, how it's different/new/novel. Putting it politely, I place very low value in how it makes some random people "feel" or what sound effects it causes them to emit, and the fact that that comprises the sole content of the video makes the whole thing suspect.