The game now has its own handbook — a 3D book waiting on the shelf right beside the radio.
So far the book covers the essentials: each game mode explained (the built-in engine, external UCI engines, and Lichess online play), plus the controls and features that are easy to miss — moving the pieces, trying out variations with the middle mouse button, switching clock models, the side UI, copying your PGN, managing engine profiles, and more.
Reading it is simple: hover over the book and it leans toward you, click and it slides up to reading position, then click the pages to turn. Press ESC or click outside the book to put it back — and once you've turned the last page and the back cover is closed, one more click returns it to the shelf.
The handbook's contents are not quite complete yet — new pages will be added.