Cool, I love Just Cause 2. I will be keen to see how the combat mechanics turn out because what makes JC2 fun is that you can abuse physics within limits to do fun stuff. In RPGs, it's more difficult to create limitations of physics-abuse because everything is set in one's imagination!
I'm actually working on a flash game (that will remain true to the tabletop game mechanics as far as possible, barring inventory and weapon details which are stripped down for sanity's sake, and because it's my first flash game and I don't want to kill myself yet) as well as the tabletop game to sort of validate my ideas in both settings.
Combat currently works based off a system of caps and randomness;
Players roll accuracy to determine if they hit. The result of this is limited by their weapon's mobility (if they or their target are moving) and stability (which is lowered by things like burst fire).
The defender rolls to dodge, limited by his Encumbrance which is a function of the armor he wears as well as however much stuff he is carrying. This can be boosted by cover. This stage will probably be replaced by damage reduction for the flash game, but read on and you'll see why that works.
Damage is determined based off the attacker's weapon and directly modified by the attacker's roll versus the defender's. If the attacker fails their roll they usually miss, though blast weapons and maximum full-auto burst weapons can still hit (at reduced damage), if appropriate. Bursts hit based on how far the player hits above; every 5 or so points (d6-based system with 3-10 dice makes this more or less reasonable) counts as an additional hit, but are not modified (or are moderately modified) by the attacker's accuracy.
Damage is compared to the defender's Damage Threshold; if enough damage is taken the defender takes a Hit. Additional bullets are handled separately, but get little (if any) of the accuracy bonus applied. For every half of the Damage Threshold the weapon does, it deals another Hit, up to the weapon's Maximum Hits (typically damage/5 for the weapon, but more brutal weapons may do more, and weapons that have high penetration (i.e. .22 rifle) may be statistically lower at damage/10 or even worse). In the flash game, this is replaced by the need to do a certain amount of damage within two seconds for most foes to kill them outright, though bosses or tough foes may take multiple hits.
Unfortunately, there is little in the way of physics abuse, but one potential use of Guts, which is sort of an Edge/Action Point system could be to generate environmental hazards.
Kyle, Head Honcho of Loreshaper Games
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