It is my sons 7th birthday today and it has become a tradition to do a paper craft electronics card for him. These have tended to get a bit more complicated every year so there is a warning there to start simple! This one uses an ATtiny 84 chip programmed via an Arduino to run a seven segment display from a 3V button cell. I used very thin kynar wire and copper tape for the connections to make it count up to and flash his age. Definitely one to do before they reach double figures!!
It would be great to print the circuit outline onto the card to scale and do some nice design on the computer, my drawing (and writing!) skills are somewhat lacking!