This game has really brought out something my father made in 500 BC
A floating shelf is a form of shelf with its wall fixings hidden within the shelf board, with no visible supporting brackets. A floating shelf may have two or more channels open from the back towards, but without reaching, the front, into which slide fasteners attached to the wall, typically held in place by screws inserted through the bottom of the shelf.
For typical floating shelf supports, a supplier suggests that floating brackets with a diameter of 12mm can support a shelf at least 22mm thick loaded with 20kg, and 18mm brackets can support 30kg on a 28mm shelf.[1]
This description is in reference to one particular type of floating shelf support, others options are available. Also not to be confused with corner shelves, which would require entirely different supports to make them "float".