Now, an incredibly complete collection of illusions called Eye Illusions has come to the iPhone and the iPad. For this review I've tested the iPhone version, which sells for US$0.99.
The illusions are in categories, like disappearing objects, weird lines, color illusions, etc. The app has something my books didn't have -- video. There is a great collection of videos of seemingly impossible objects. You watch the video, and then you get a look behind the scenes to see how the illusion was accomplished.
The app gets updated with new illusions all the time, and you can share them, although the email you send is constructed as an ad for the app rather than a link to a particular illusion.
It would be easy to lose a few hours in this collection. I enjoyed seeing some of the illusions I loved as a kid, and seeing a vast collection of things I never knew existed.
The only downside to the app is it is not universal. If you want it on your iPad, you have to spend another $0.99, and I would expect the illusions to look really great on the larger, high resolution screen.
If you just want to get a hint of what this app does, you can download a free limited version here, but if you are really an optical illusion fan, you'll want the whole deal.