## Unit Movement

Movement is the most important action type. There are actually two distinct types of actions; one to enter a cell, and one to enter a unit.

Each unit has a speed which is determined at the beginning of the turn and determines how many cells it can enter during the turn. However, terrain, borders, and other obstacles can consume extra movement points.

### Unit Speed

Units have a base speed `speed` which is the ratio of mp to acp. You can set damaged units to move more slowly. You can also allow occupants to add to the speed, up to the `speed-max` limit.

You can define wind-affected units by defining speed in each direction (max-speed only, do others proportionally). Would need 4 distinct mp costs plus a formula to relate to wind strength. Wind speed defined as "how far a particle of air moves in a turn". Unit examples include balloons, dirigibles, sailing ships, floating cities.

### Movement Costs

Typically the cell entry cost will be the most useful to adjust, although the departure cost can be useful in representing units mired in jungle mud and taking a long time to escape onto clear terrain.

Be aware that complicated entry/exit costs are confusing to players, and AIs may not take them into account very well either. Using `free-mp` helps players use up all their acp.

### Entering Transports

Different kinds of transports have different ways for units to get on and off. For instance, ships can dock, or use their boats to enable land units to get on and off. The tables `ferry-on-entry` and `ferry-on-departure` specify how much terrain units will have to cross on their own.

[example]

Observe that enter/leave costs can be used to make one-way trips. For instance, paratroops jumping out of a plane should be able to leave cheaply, but have an entry cost so high that they can only reboard in a later turn.

### Border Slides

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.

### Leaving the Area

This feature can be useful in allowing a non-disbandable unit type to escape capture or otherwise retire from action.

### Free Moves

This is most useful in emulating some board games, or to prevent clever players from exploiting a mess of move costs. The default of `-1` is the most playable, since player will always be able to use all of their mp. Otherwise, there may be situations in which a unit has a few acp left, but not enough to go anywhere, and so they end up being wasted. The free move does not actually get subtracted from the unit's acp, it just doesn't let lack of acp forbid the move.

### Zone of Control

Sometimes a unit can by its presence alone affect the movement of unfriendly units in the vicinity, perhaps by requiring them to hide or to move carefully in order to pass by, or even to prevent entry altogether. This is called the "zone of control" or ZOC.

Exerting a ZOC requires no action, nor any particular capability on on the part of the unit exerting the ZOC. For instance, a toothless fort could still cause raiders to sneak by carefully (at least if they didn't know that it was toothless).