Finally got 'round to populating the business cards and fixing a few errors. I missed a few grounds on the logic gates, which was no big deal to fix, and found that the SEEED Xio SAMD21 MCU could not drive the buzzer directly and so had to switch in a ZTX 450  NPN transistor, which worked ok. Although the circuits 'kind of' worked, it seems that I have damaged the MCU, which is a bit annoying (pun intended)  probably trying to drive the buzzer, so that needs to be swapped out for a new one. Strangely, the buzzer still works although pin D1 now thinks it's D2, which is very strange. Pin 13 also works, powering the onboard LED, but none of the other pins seem to work. Hopefully easy to fix once the MCUs arrive from Digikey. Plenty of time before the competition finishes although fairly sure it's not going to win anything :(