Draw an optical illusion

Watch this video...it's pretty cool.

I had a go myself but I don't have a black felt tip at home so I just had to colour it in with a black biro (my arm hurts now!). If you don't have any black pens at all, I think you will just have to colour all the black bits hard in pencil with no white. Let us see how you get on  by sending a picture to debeauvoirprimaryschool@gmail.com

Here's my effort: