More about my stacking architecture in this article:
hackster.io/news/the-armachat-nano-racks-up-the-features-by-stacking-up-pcb-pieces
Video presentation:

Main board top/bottom


Optional USB-A host board


Middle board for joystick

Top touch board ST7735

Top touch board ST7789

Middle board for games

Middle board with QWERTY keyboard

Side spacer and layer connector

Fascinating! I just loved the curved tracks and the possibility of using the other side.