Ok I'll look into this. Please let me know more info to help the debugging.
When I swap monitor, the background turns black on my main monitor, and clicking on the black part make it transparent temporarily, and click on on the cat/book makes the bg black again. Restarting the game fixes it for me. Does that happen to you all?
What's the OS (Win7/8/10/11)? What's your Graphics card? Resolution? Single or multi monitor setup?