My 10-year-old has my old Nintendo DS Lite (one of their best handhelds, IMHO) and has been inheriting my games one or two at a time… it’s got to where he needs a better place to store them all.
The box is mostly direct from boxes.py’s flexbox3, but with a couple of tweaks: two shelves, kept in place by grooves engraved in the sides, with just enough slots to hold all the DS and GBA games my son will eventually inherit.
The higher shelf is at just the right height for a GBA or 3DS game to rest on its protruding tabs, then another slotted shelf at the bottom keeps everything standing up straight.
One other tweak: After prototyping this in draftboard (which means I have an extra box for storing the games yet to become hand-me-downs 
), I found the hinge needs to really stretch for the box to fully close. I didn’t change the lid dimensions, so it still needs to stretch, and gets a snug fit — but I added a couple extra rows of cut lines to the living hinge so it can stretch with less stress on the material.
The box is 
cherry plywood, and the shelves glass-green-edge clear acrylic (Inventables, since I haven’t caught the proofgrade version in stock).