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

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:

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.

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).

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).

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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