I needed a game card holder for all my Nintendo Switch games and of course I had to over-engineer my own. ;-)

Features:

• room for 16 game cards: four slots each on top and bottom; double sided (backside not pictured)
• see which game is which at a glance, thanks to acrylic glas top cover
• (strong!) magnetic latches
• NO GLUE! :-D

The design is pretty flexible: It should not be too much effort to modify it so as to have have it one-sided or only one lid per side (or one lid, one side) – originally, it was designed for only three game cards per row. I wouldn't recommend it, but it's possible to add more cards per row…

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Materials:

• laser cutter
• 4mm HDF (~15x38cm)
• 4mm acrylic glas (~6x30cm)
• 20mm screw posts (6x)
• 12x4x2mm Neodymium magnets (16x)

Lasercut everything in the SVG. Ensure to first cut out the holes (red lines), then the shapes (black). The blue shapes (with pink holes to be cut first) are the acrylic glas parts.
(The light blue slices are just placeholders for the magnets, in case you don't want them or want to use less than I did.)

I used 4mm HDF (game cards are ~3.4mm thick according to my measurements, which leaves a bit of wiggle room for the cards – perfect!), as well as 4mm acrylic glas for the top and bottom to see the content even when closed.
Then, after semi-assembling everything, I inserted the magnets (partly stacks of two and three) into their slots. The length of the magnets ensure that the middle "spacer" parts stay fixed in place. (Originally, I had different magnets that weren't nearly as strong; that's why I added stacks of magnets to the design. Now it's almost too strong – on the other hand, it ensures that it doesn't open when carrying in a bag or something.)
Finally, the screw posts are screwed together (with a bit of threadlocker to fix them together while allowing the covers to rotate).

Works like a charm!

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Picture information:

• finished product (3x)
• visual assembly guide
• (very) first design sketch
• clamped-together, one-sided, single-row only, beta version

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Room for improvement:

• a couple of mm's in thickness could be shaved off from the finished product by choosing thinner top, middle, and bottom layers (both HDF and acrylic glas; the layer with the game cards needs to remain 4mm); note that the screw posts would have to be changed and not all lengths might be available
• magnets … I don't like the asimmetry, but it has its reasons; the batch of magnets I used in the final version are very strong, probably could remove a couple
• the inner layers of the lids are fixed in place by the magnets on the narrow end – works kind of OK, but it could be better; maybe shave off a mm at the edge?