Literally “box of cards”. System to organize notes and ideas. The key aspects:

This system is supposed to maximize serendipity and ability to make connections (networked thought) and inspires to produce original content just because unexpected realizations happen when building it.

The digital translation you are reading is a labyrinth of ideas, which is the same thing but in website form.

Something is lost when we don’t have the physicality of cards, but also something is gained: can this be gamefied?