Modular Raspberry Pi Cluster Case

Here's yet another Raspberry Pi case! This one is a little different. There are several requirements I made for myself and this hit (almost) all of them:

1. *No hardware required*—everything should snap together, no screws/nuts required
2. *Modular*—can print 1, 2, 3 or more and stack them together
3. *Open for airflow*—I prioritized air flow and cooling over a completely hard shell
4. *Fits most HATs*—each module is 30mm tall which should be enough room for most common HATs
5. *Quick to print*—most printers should be able to print any one part in less than 2 hours
6. *No supports when printing*—like most people I prefer not having to print supports and then remove them later (often leaving behind ugly evidence of where the supports were). I was almost able to achieve this, although you'll see from the images that 2 tiny supports are required where the fan mount pegs are (but they break off cleanly)
7. *Can mount a fan when stacked*—in the 4 Pi configuration there is a special