Summary
Designed with the following constraints:
Holds up to 12 Nintendo N64 games
Fits inside a standard Ikea box shelf
Games can be picked out and placed back without knocking others over.
3mm ply
The tolerance is tight on the tabs, and the 3mm ply I used was more like 2.9mm. You may like to open those up a bit, depending on how accurate your laser cutter is.