>Ok, your turn :)

I'll give you one:

I show you a closed door to a room. In the room are three light bulbs, all turned off. On the outside of the door are three light switches, one for each light bulb. Each light switch is in the down position. You cannot see into the room. You can manipulate any two light switches on and off as many times as you like. When you are done, you are to open the door and tell me which light switch goes to which bulb. Once you've opened the door, you cannot touch the light switches again. How do you solve this problem?