Traffic lights

This was my second task given by university, the task was to develop a working pair of traffic lights using only logic gates, counter and 555 timer. To get higher grade you have to design the system with least amount of chips.

Me and my friend found one of the best solution. Basically by merging together karnaugh maps, boolean algebra and deMoragns theorem, we managed to design a system which only uses 3 logic chips. I don't remember exactly which ones we were using, I have to check my logbook then, but if I'm remember correctly 1 AND, 1 OR and 1 NOT chip. By combining them together we could make NOR or NAND gates and use all the pins on those chips.