Installing a thermostat

Our house came with an old, mercury thermostat,

This is non-programmable, so either it's always too hot, always to cold or you're always changing the temperature manually.  So we bought a replacement.  First I took off the old one.  You can see the mercury bulb in this picture:

Behind the actual thermostat was a pretty cool-looking network of wires.  I'm not sure why it needed to be this complicated, considering that there were only two wires coming in...

You can see that the mercury thermostat was at least the second installed in that location.  After drilling some holes, installing the new one was as easy as attaching those two wires to the new thermostat, attaching the thermostat to the wall and putting in batteries.