Update: a new post on this subject.
And here is is: Find the gnomes
After just 2 weeks the idea has landed and the crowd is applauding: a search and find game where you chase garden gnomes.
A gnome and its collision window in Alpha 0.1.1:

And a peek at the art style & level design in Alpha 0.1.2:

The alpha testing has been a success. A lot of positive reactions on the core game mechanics from young people to elder ones.
There is still a lot of work to be done so the update continues!
The next official project update is scheduled at 18 February 2018, we will hit version 0.2 by then. It will include a bit of everything: a basic start menu, the basic in-game interaction counters, minimal special effects on objects, a level ending, an achievement system.