Absolutely superb. And I'm doing an optical illusions special with my students this week too so this goldmine is perfectly timed. Thanks! My favourite are the

Absolutely superb. And I'm doing an optical illusions special with my students this week too so this goldmine is perfectly timed. Thanks! My favourite are the colour ones. I stare and stare at them trying to isolate the bit that - for example - is actually grey but looks red, to see its "true" colour. That level of concentration...not really ever seeing the grey, but perhaps objects behind me in the room flying around Matilda-style.