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Old 09-20-2018, 04:06 PM   #2
Dalin
 
Join Date: Dec 2009
Location: Saint Paul, MN
Default Re: Moving fast through difficult terrain

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Originally Posted by coronatiger View Post
How do I model running through difficult terrain in GURPS, like cluttered backyards, building sites or wrecked buildings? I don't want to spec up every obstacle, but could assign a general difficulty to the area (and the players could reduce the difficulty with Per rolls to find a smart route).
Interesting challenge. I'm tackling this without my books, so I can't cite precedent or parallel rules. Here's how I would do it:

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1. How often should I require the players to roll?
I would choose something that makes sense dramatically. If you're not in combat time, then I could see 2-4 rolls for 100-1000 yards.

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2. Which skills should I allow/require? I'm thinking that Climbing, Jumping and Acrobatics are viable options, possibly Running. Are there other skills that could be used?
3. Should I assign different difficulty levels to each skill depending on the type of obstacles?
My instinct would be to use DX or Acrobatics as the base skill with a flat penalty for my sense of the difficulty and allow the player to pitch another skill as a complementary skill roll. (Maybe the Per check could also be complementary.) Depending on their pitch and the nature of the obstacles, I might allow the complementary bonus to be double (+2 instead of +1, or +4 on a critical success).

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4. How do I determine how quickly the characters traverse the area?
Well, you know the theoretical top speed for a straight line sprint on clear terrain, so that's the upper limit (e.g., for a typical Move-5 person, they can sprint at 6 so they could cover 1000 yards in 167 seconds). Reduce to whatever makes sense for the terrain. I might think of this in terms of combat time; if, in combat, a character would have to spend 2 extra movement points per turn (on average), then this would reduce top speed to 4 yards per second, giving us 250 seconds for 1000 yards. Or just handwave and pick a number that seems plausible: "Moving fast, with a bit of luck, it'll take about five minutes."

Then adjust based on the skill rolls. Could be simply reducing it a bit for each failure (-10% per failure on four rolls). Critical failure(s) indicate a serious mishap, so you drop out of the race. Or you could come up with something based on the margin of success. That would take a bit more fiddling with odds to come up with a spread that seems reasonable. Critical successes allow you to come up with an unusually clever shortcut that speeds things up (or counts as two successes).

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5. How could familiarity with the terrain reduce time spent and/or difficulty?
I would adjust the base skill modifier for this. So if you live in the junkyard, you can sprint through it at only -2. The thugs who tried to ambush you there are at -5.

That's my initial take. Curious to hear about other ideas and/or tweaks.
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