Today you're going to photograph objects ... people ... buildings ... whatever, but you can't show the actual object in the shot. That might mean you're using its shadow, reflection, imprint...stretch your mind to find a way to photograph things without them being in the shot - remember it can be anything generated by the subject...but it just can't be the actual subject.
If you've just joined us, February is a 28 day creativity challenge with a new "prompt" each day to get you thinking in new ways. The goal is to just have fun, don't try to control too much, feel free to use a cell phone or any camera that's easy for you. Don't worry about the end results. With each prompt you can take it literally or not, you can wing it, google it, ask for people's opinions...whatever you want to do is perfect. Bottom line - it's supposed to be fun, there are no right or wrongs.