An interesting illusion of my own creation

Is the blue box truly a box or are the lines bent? Clicking the image will open it in a new window with a white background and you will see only the box itself.

Remember that commercial.....

....where the dad is looking for his son and can't find him because the son has climbed up the wall. I have no idea what the actual product was, oh well. Anyway, Harrison surprised me one day by climbing up the wall. These pictures were taken on subsequent climbs, so it wasn't just a one time thing. I am so glad that a 3 1/2 year old is able to figure out on his own that his hands and feet can touch opposing walls. He further discovered, completely on his own, that by putting pressure on those hands and feet he can go up the wall.