Can't remove light cover
I know this is probably a dumb question, but I bought this house last year. There's a light in bedroom with two bulbs, one of which just went out. I was going to replace the bulb, but can't seem unscrew the cap or take it off. The cap is sort of round and flat, and I don't know how to take it off. I suppose I could force it, but I thought it better to ask and look like a fool, than break it. I included a picture. It's not the best picture, but hopefully it'll help. Thanks.