My parents share a Mac Mini. Often when I'm at their house, I notice that it's been left at the login screen. Presumably one person logged out thinking they were leaving the computer available for the other and then never put it to sleep at the login screen. The issue is that Energy Saver prefs don't seem to apply when there is no user logged in. The computer just sits there with the login window display indefinitely. It never goes to sleep or turns the display off. Is there any way to have some sort of daemon run only while no one is logged in that would either shut down the computer or put it to sleep after a specified number of minutes of being idle at the login screen? While the Mac Mini is a very energy efficient computer, it still makes no sense for it to be on for dozens of hours each week unnecessarily. Any ideas?