Unlock Small Doors on a Grid

So I have an idea of a habit builder (also I think it would be fun to build)

Essentially, one piece tracks the habit, and one piece unlocks doors (small, in a grid) based on habit trend. Inside each door would be a "prize".

My question is about the small doors.

• Is there an example of small unlocking like this I can use to expand to multiple doors?

• The idea is there might be more doors than pins on the microcontroller. Is there a board I could put inbetween, or a special technique since they are on a grid, to accomplish this?