There’s no game that takes twelve steps to resolve an attack. That’s as much an extremism as describing light games as just improv theatre.
I count 11 steps in Shadowrun, though you could argue that some of those steps are actually the same step (much like you can mush together different calculations on the same line in physics). I don't count the attacker's choice to attack and how, but I
do count the defender's choice of defense.
1. Defender chooses how to defend.
2. Attacker rolls relevant combat skill + modifiers.
3. Defender rolls relevant defense.
4. Net successes = Attacker's successes - Defender's successes.
5. If Net successes <0, the attack misses. If >0, the attack hits. If =0, the attack is a grazing hit that does do direct damage but does connect, in case that's relevant for things like touch attacks.
6. Modified damage value = base damage + net successes.
7. Modified armor value = base armor - Armor Penetration (minimum 0).
8. If modified damage < Modified armor, the final damage will be Stun damage, otherwise it's Physical.
9. Defender rolls Body + modified armor value and reduce the damage taken by the number of successes.
10. Apply the reduced damage to the Condition Monitor.
11. If the damage taken > defender's Physical Limit, defender is knocked down.
There's also the previous version of the Swedish game Eon:
1. Attacker chooses whether to make a forceful attack (more damage but easier for the defender to gain initiative and thus become attacker the next round), quick attack (the opposite), or a regular attack.
2. Attacker secretly chooses whether they want to attack in a high, medium, or low position. This affects hit locations and possibly the defenders difficulty.
3. Defender chooses whether to ignore the attack (usually a bad move), counterattack (also usually a bad move unless you can rely on your armor), parry (with a weapon), block (with a shield, easier), or evade. There are also a number of other options, but those are usually not done in response to an attack.
4a. If the defender parries or blocks, they may secretly choose whether to defend in a high, medium, or low position. If they do, and choose the same one the attacker did, the defense becomes easier. If they choose wrong, the defense becomes harder.
4b. If the defender evades, they may choose to sidestep, back up, duck, or jump. If they do, the defense may become easier or harder depending on what sort of attack the attacker does (slash, pierce, crush) and/or what position they attack in (sidestep is good against piercing attacks, ducking is good against high attacks).
5. Both attacker and defender roll their relevant skills.
5a. If the attacker succeeds and the defender fails, the attack hits.
5b. If the attacker succeeds and the defender successfully parries or blocks, the attacker may damage the defender's weapon. Roll damage and compare it to the weapon's/shield's durability. If the durability is higher than or equal to the damage, nothing happens. Otherwise, reduce durability by 1 and roll a durability check (difficulty depending on how much higher the damage was) to see if the weapon breaks.
5c. If the attacker fails, or the attacker succeeds and the defender successfully evades, the attack misses.
6. Roll damage.
7. Check for knockback (even if the attack was blocked or parried).
8. Roll hit location (of which there are 26).
9. Reduce damage by the armor on that hit location.
10a. If remaining damage is less than 10, apply a small number of points of Pain, Trauma (=actual things that break), and Bleeding, depending on hit location and damage type.
10b. If remaining damage is 10 or more, roll a d10 to see what kind of critical injury you inflict. Check the critical injury table to see how many points of Pain, Trauma, and Bleeding you inflict (usually by multiplying/dividing the base damage by some number). Also see if there are any special effects from the critical injury (e.g. amputation, scarring, falling, etc.).
11. Apply any special effects from the critical injury, and potentially roll for them (e.g. an "Amputate" results means the defender needs to roll to see if the body part in question is chopped off, which then either adds more pain/trauma/bleeding or in some cases kills you outright). This can be multiple steps in some cases (e.g. if you both need to roll to see if you lose your limb, and then if you can remain standing).
12. If Trauma was inflicted, the defender rolls a Death check.
13. If Pain or Trauma was inflicted, the defender rolls a Consciousness check.