Need better explanation of interface

[genseirin]

There is that "play" / "stop" button (using Mac) which seems to start syncing when I switch to "play" and then, after some time, falls back to the "stop" position. It is unclear what it actually does, since the app should watch anyway and sync automatically when ever there are pending changes. So should I keep the "stop" or the "play" position to keep my devices in sync? Is it due to the "issues" (= zero-size files) that it drops back to "stop"?

Similar apps have "pause" and "resume" states, which makes more sense to me.

It would be good to have tooltips for buttons or at least explanations in the online documentation.