 single outside or
inside corner, a side, or completely filled. To place the icons correctly,
each must be part of a 2&times;2 block. Also in any given 3&times;3 block,
there may not be two empty corner tiles, since this would require the center
icon to have two inside corners.</p>

<p>Another type of join based on this, Neo-Foomerian joining, uses 15 states.
It has the same restrictions except for one: it allows icons with two inside
corners. This form is a little easier to work with when building maps, bu