Hello everyone,

I just read about this site in Videogame Careers by David SJ Hodgson, Bryan Stratton, and Alice Rush as the book told me this would be a good place to network. But my abilities are not up to a proficient degree as of yet so i'm still going though the basics and designing pen and paper games to get the fundamentals down. Here's my problem;

I'm trying to design a D20(ish) version of the Mass Effect series. For those of you who have played this franchise, you fight using cover based, third person shooter combat. The problem is translating that feel onto pen and paper. I have basic class write ups, abilities, races, basic weapons, etc but my problem is designing a cover system that would keep the momentum of the fight going so my players aren't constantly in a cover stalemate with enemy NPCs. My idea is a "gambit" (code name) system that wouldn't penalize you for being in cover but would give the players bonuses against enemies who stayed to long in cover (as you know their position and can plan accordingly). Cover also has different grades ranging from Inferior (20% Cover) to Total (100% Cover). You can hit an enemy by rolling a percentile (a d10 with single digits and a d10 with 00 to 90) and if you roll above that cover's percentile, you hit them (still working out mechanics for shotgun and smg as for spread fire and multiple shots). The "gambits" are as follows;

First Round behind cover: No bonus
Second round behind cover: (Undecided, possible bonus for those trying to flank this target)
Third round behind cover: +20% to Hit target
Fourth Round behind cover: Attack of Opportunity-Should the opponent behind cover commit any action that momentarily breaks cover, any player committed to attacking said target is allowed on free attack, regardless of initiative, if able to do so (i say committed to attack in thinking that any player who has them in their sights with at least one shot in their clip)

Note that this would also work against players giving them incentive to keep moving on the battlefield. What do you guys think and do you have any suggestions?

Designing any game, whether it's pen-and-paper or electronic, is fundamentally about iteration.

You want to start with a base concept, even if it's really simple or only a fraction of what you envision for the completed game. Get it implemented and playable as soon as possible. Then start playing it, and refine it as you go along, introducing new elements from your grander vision as things progress. Oftentimes you'll find new ideas along the way, or discover that your old ideas weren't as good as they sounded on paper. Either way, the trick is to keep playing the game and tweaking it based on your experiences.

I've been part of a few pen-and-paper game designs, and played a fair number of tabletop RPGs, and this is the most surefire trick I know of for getting a good experience out of a game. Just play the heck out of it and the problems (and strengths!) will become very obvious, and you can go from there. Spending too much time theorizing is just a waste of effort, past a certain point, because in the end nobody can really predict how a game will play just by reading the rules. At some point we have to jump in and give it a shot.

Moving to Game Design. This isn't a programming question.

Rather than ad-hoc "gambits", I'd use opposite "combat sense" skills of knowing when to leave cover to attack (enemies are exposing themselves) and knowing when to keep cover to defend (you are about to be attacked). The combatants with bad skill rolls are going to shoot into empty space, or to be mowed down when they move.
Damage reduction or a chance to miss according to cover effectiveness should be layered on a traditional die roll to hit (and possibly also a defense roll to dodge or parry): aiming right when running, ducking etc. isn't trivial.

I'm not sure just how close to D20 you're looking to model this, and it's been many years since I've touched anything D20 related, but the attack of opportunity sounds like a reasonable way to handle it. If a character observes a piece of cover long enough and is expecting someone to pop out and take a shot or run for another piece of cover, they get a shot at them as soon as they make the move.

I'd say that adding other bonuses for staying behind cover too long might be a bit more trouble than they're worth though.

If I were handling it, I'd probably do something like this:

1st round: No change
2nd round: Cover bonus is reduced by 1 (assuming you were using a D20 style AC system, and cover added to AC, I don't recall honestly)
3rd round: Allow attacks of opportunity when the character leaves cover, negating any cover bonus

In D20, that would represent almost 20 full seconds of observation, so it sounds reasonable to me.

In order to allow this, I'd require players to spend full rounds observing the target though. Whether this is worth it or if they should just spray the area down though is going to depend on a lot of things.

As ApochPiQ said though, you'll just have to playtest it. Any problems should become evident soon enough.