the top part of the case had its rectangle centred on the y-axis rather
than on the origin directly, which had a cascading effect of being
unsymmetrical, its origin hitherto unknown.

- tolerances still too tight, bottom wasn't proper (symmetry broken
  somewhere so had to change how the bottom attaches to each other).
- change tolerance of bottom to 0.6mm, and of nubs to 0.3mm.

- make walls 5mm thick instead of 4mm thick.
- forgot to make bottom smaller than top to fit smoothly; gap in bottom
  for PCB also didn't account for tolerances.
- make feet on bottom a bit bigger and adjust hole position.
- make USB-C port cutout bigger, as, in practice, some cables are still
  a tiny bit too thick to fit the hole.