My room is a closed system: what can get in?

I shut all the windows and doors. I shut the vents and turned off the air-con. My room is a closed system because particles can't get in or out. But the temperature can change. How so? In a closed thermodynamic system, heat and work can cross the sealed boundaries when particles can't. In other words, energy can cross the boundaries. Traditionally, we say heat and work. At GCSE, an attempt has been made to interpret that. Work has been interpreted as MECHANICAL WORKING and ELECTRICAL WORKING. Both are valid interpretations of work. Heat has been boiled down to HEATING BY PARTICLES (basically conduction) and HEATING BY RADIATION (infra-red would be the obvious example). So I asked my class what could get in and out of my classroom. Good answers named the two interpretations of heat - with the Sun streaming in through the window, one was obvious. I hadn't expected work, because the room doesn't expand or contract. But my smartest added ELECTRICAL WORKING. And she's right! Energy was coming into the room from outside to work the lights. I'd missed that.