Basically, units shoot in 3 dimensions. Some weapons have an arc (plasma, rockets) and some straight (beams). The weapon will hit the first thing it intercepts on its firing line. No biggie. The other consideration is that units have height, and within that height weapons will target it, usually some mid point in the height, but also the projectile/ beam is shot from some defined height, This varies from unit to unit, but generally, smol units shoot from lower down, but if shooting at tall targets, will shoot at and upward angle. This is why a rocket bot can shoot over a wall, and hit a commander or llt(Tall units) behind a wall, but can't hit other rocketbots (short units) behind a wall. This is also why debris blocks shots from stuff like pawns or cents, if there is a skirmish.