Create/Draw an optical illusion. Below are some ideas. You can re-create one of these or creat one on your own
https://www.youtube.com/watch?v=WlxWWjlqFpw
https://www.youtube.com/watch?v=kZHIzia0jz8
https://www.youtube.com/watch?v=6TCKUalhvYI
https://www.youtube.com/watch?v=d4dPnNERqzs
https://www.youtube.com/watch?v=OM9oYcdIJaM
https://www.youtube.com/watch?v=KfFBSeFbtp0
https://www.youtube.com/watch?v=WlxWWjlqFpw
https://www.youtube.com/watch?v=kZHIzia0jz8
https://www.youtube.com/watch?v=6TCKUalhvYI
https://www.youtube.com/watch?v=d4dPnNERqzs
https://www.youtube.com/watch?v=OM9oYcdIJaM
https://www.youtube.com/watch?v=KfFBSeFbtp0