An AMBIGRAM is a word or a sentence that is written such that it becomes readable in more than one way. 

For example, if your name is HENRY, then

is an ambigram of your name; it stays unchanged when you turn it upside down. 

There are many more types of ambigams. EYE TWISTERS is a collection of 200 + mostly original ambigrams. The following page contains more examples of the different kinds of ambigrams in the book. Push the animated `Next' ambigram to proceed. 

The picture in the middle of the cover is M.C. Escher's "Eye" (c) 1999 Cordon Art B.V. - Baarn - The Netherlands. All rights reserved.