An attack is obstructed if the attacker measures range through an obstacle. If an attack is obstructed, the defender rolls one additional defense die during the "Roll Defense Dice" step.
An attack is either obstructed or not obstructed; the number of obstructions does not change the number of additional defense dice rolled.
Small and large ships do not obstruct attacks.
The attacker cannot attempt to measure range to a point of the defender's base that is not the closest point in order to avoid measuring through an obstacle. If mulitple points are at equal distance from the attacker, he may choose one of those lines for measuring range.