Cover, Concealment and posture (CCP)
Cover, concealment and posture all impact the difficulty in hitting a target with a ranged weapon. The differences are
Cover - Putting a physical object (rock, building, vehicle, etc.) between you and the projectile.
Concealment - Obscuring one's position (bushes, camouflage, cloaking device, etc.).
Posture - Body position.
The effects of CCP on combat are described below:
Cover:
If a suitable "cover" object is available, a player may select a cover value from 0 to 6 where 0 is no cover and 6 is maximum cover.
In combat the defender's cover value is subtracted from the target number (TN) decreasing the likelihood of a hit. In addition, 1/2 of the the attacker's cover value (rounded down), is also subtracted from the TN to account for the difficulty in firing from a covered position.
In summary:
Defender: More cover = Better
Attacker: Less cover = Better
Note that the "suitability" of cover depends on the weapon. A mirrored surface, for example, might be suitable cover for a laser weapon, but not for a bullet.
Concealment:
If concealment is available, the defender's concealment value is subtracted his/her "size". This reduces the "apparent size" (size - range) and decreases the likelihood of a hit. If the apparent size is reduced to zero, the defender cannot be seen. There is no penalty for an attacker with concealment.
Posture:
Posture is the body position from which one is attacking or defending. Posture may be "Upright", "Crouching", "Prone", or "Evading". In combat the defender's posture effects the TN with the following modifiers:
Upright 0
Crouching -1
Evading -1
Prone -2
There is no penalty/advantage resulting from the attacker's posture.