I remember that was my first experience with the Nokia N9 (spiritual and technical predecessor of the Jolla phone).

At the store, I picked it up, turned it around a few times to confirm that there are indeed no buttons, then tried tapping the screen all over but it stubbornly displayed only a screensaver.

Later someone told me that I was supposed to rapidly tap twice in one place (like a double-click on the mouse) to get to the home screen. Nothing in the unit's physical design or software suggested this.