(currently retired)
PatCzeckers contains pictures, not letters. The pictures make little sense in themselves because they are meant to be used to create patterns. In PatCzeckers the characters are meant to be combined in a checkerboard pattern, as the name suggests. The layout of the characters is simple; the parts of the pattern are on the same key, one on the lower-case selection and one on the upper-case selection. To form a pattern, one must type in a sequence such as AaAaAa on the first line, then aAaAaA on the second line. This pattern can be repeated as many times as one wants. It is not as confusing as it sounds, and the effect is very interesting.
The characters on the number keys are more complex, because they are in an enhanced checkerboard pattern. The complete pattern is made up of four pieces, two of which are in the character set above 127.