I’m still waiting for something to test my colleagues. What’s the answer to the lightbulb one? Time is running out… I need to uphold the (supposed) levels of British intelligence!
A light bulb actually has 2 digital states (on/off) as well as an analogue state (temperature). In this sense you could differentiate between off bulbs by comparing their temperature so you could work out the switches for more than 3 switch/bulb combinations.