Hit Resolution
Accuracy, crits, targeting, and who soaks the damage.
THE ROLL
Every shot targets the lowest-HP enemy inside the shooter's own range and rolls to hit. Hit chance is the shooter's accuracy, reduced by the target's evasion, adjusted by terrain (currently inert — see Terrain) and multiplied by 0.7 if the shooter's stack is moving — then clamped so it always stays between 5% and 95%. A separate roll on a hit decides a critical hit, which multiplies damage (×1.0 for small arms up to ×2.0 for anti-air). Damage is then scaled by weapon-type-vs-target-type effectiveness. Crit, effectiveness, cover and terrain together can never multiply a hit by more than ×3.
SIMULTANEOUS FIRE
There's no "attacker fires first". Every unit whose reload is done fires in the same exchange, from the state at the start of it — a unit killed in that exchange still gets its shot off. A target already brought to 0 HP earlier in the same exchange is skipped by later shooters. Damage lands on the live units immediately, shot by shot.
SHELTERING BEHIND ARMOR
Infantry and support units take half damage while a living armored or naval unit is in the same stack — infantry sheltering behind armor. The bonus disappears the instant that protecting unit dies.