Footprints:
- avoid non-circular holes in footprints whenever possible; some fabs charge more for ovals

PCB layout:
- make power connection traces larger; MK uses .6mm
-- this means from the IDC through the power safety block and into any non-high-impedence connections; that is, fat traces to chip power, but not necessary for voltage dividers feeding chip inputs
- don't do manual connection to GND if you can avoid it.  wait and use a ground plane.
- when two traces cross on opposite sides of the board, cross at 90° to minimize capacitance between traces
- vias connect through the board, connecting a trace on one side to a trace on the other

Ground planes:
- ground planes are copper fill applied everywhere there isn't a trace already
- use spokes where ground planes connect to holes - these gaps reduce heat conduction during soldering
- ground plane spokes can be the same size as traces - .3mm for non-power lines, .6mm if carrying power
- MK uses a ground plane on only one side when convenient.  You can use one on both sides, or do partial planes where convenient.

