The key ideas so far are the center placement of high frequency keys and the double oversized space keys. An additional degree of optimization results from that of key-to-key transitions. This was done as follows:

	Measuring frequency of letter-to-letter transitions
	For a representative corpus of the English language - several millions of characters - we have measured the frequency of letter-to-letter transitions. For example, this produces the number of times the letter o is followed by the letter a.
	Rearranging the keyboard layout
	Then we have rearranged the keyboard layout to minimize the average travel. The effect of this optimization is that the most frequent key transitions are between adjacent keys.

The best keyboard for a representative corpus of text is not unique and the choice among keyboard layouts of similar efficiency was then based on other grounds such as mnemonic considerations. For example, the keys of the selected keyboard offer easy to remember sequences such as fitaly, doors, and jump; and vertically, count and harem:

Note also, that the keys are easy to find since the next letter that you are going to type is most likely to be one that is adjacent to the one you just typed. This ergonomic and mnemonic advantage comes as a consequence of having optimized key-to-key transitions. This is quite apparent in the following examples:

For the FITALY layout, we have obtained an average travel of 1.8, to be compared to an average travel of 3.2 for the QWERTY layout. (For prose, involving few numbers and symbols, the results are even better.)

As a final example, try to type do it with a pen. Jump from letter to letter with one finger and make sure that you use the closest space key between words. You will see that this can be achieved with very limited pen travel on the FITALY keyboard:

Fitaly:	Qwerty:

As you can see, the pen travel is about three times larger on the QWERTY on-screen keyboard.