One of the problems with Xconq borders and connections is that
neither works exactly like a sea strait. Consider the Straits of
Gibraltar. They are so narrow that one can see the other side,
but nevertheless impose a formidable barrier to landlubbers.
At the same time, ships can pass through readily, if
not secretly. If cells in the world are 60 miles across, then
making an all-sea cell is a gross exaggeration.
However, adding a water border only prevents both land and sea movement!
To get around all this, Xconq allows a special kind of
move called a "border slide".
Basically, if both the destination cell and the border whose endpoints
touch the start and end cells are allowable terrain for a unit,
then the unit can move to the destination cell in one move.
However, it incurs a special cost in addition to the normal entry
and leave costs for the terrain in the two cells (but not the border
crossing cost, since the border is not being crossed, exactly).
This cost is in the table mp-to-traverse
.
Border sliding should usually be somewhat expensive, both because
of the distance (the unit ends up two cells away after only one move),
and because of the real-life difficulties of passing through a narrow
strait. Note that border sliding does not escape the units on either
side of the border, since the unit doing the sliding will still be
adjacent to the cells on each side of the border it slid through.