So, humanoids can kick and punch. Everyone knows what that looks like. A kick picks your foot off the floor and uses it as a striking surface. A punch is the same with your arms.
This is all well and good for humans, and even critters like Kangaroos seem to have Boxing-14 as an innate skill. Maybe Brawling too.
But for, say, a giant spider? Can they kick? Punch? How does one work them up?
This was inspired by +Daniel Tallor‘s question about the SM of legs for a “pony-sized” spider.
Something like this (for +Jason Blalock ):
Arms and Legs
To me, and to GURPS (see Extra Arms, p. 53) if you can manipulate things with it, it’s an Arm. If you can manipulate things with it but still use it to walk, but not at the same time, it’s still an Arm, but with the Foot Manipulator limitation.
If you can potentially strike with it at full DX instead of DX-2, it’s an Arm.
If you can manipulate objects, but not terribly well, it’s likely an Arm with either No Fine Manipulators or Ham-Fisted.
If by picking up more than one of them off the ground, you risk falling down, if picking up one or more make you unstable, it’s probably a Leg. Not guaranteed, though.
The other thing you’ll want to watch for is Reach. Human arms and legs seem to be different from each other by about one step on the Size and Speed/Range Table. And while legs (for humans) have a reach roughly equal to SM-2 in yards (so 1 yard for legs for a human of SM+0), Arms seem to be treated as if they’re four steps down.
I say this because if you take someone with gigantism, their reach for their punches does not increase unless they’re wielding a Reach C weapon like many knives. If they were treated as SM-3, the one-step boost would make them one yard, and hit the Reach 1 breakpoint.
Honestly, I sorta disagree; I’d give SM+1 creatures Reach 1 with punches, but since the next step for kicks from 1 yard is 1.5 yards, they are Reach C, 1 for both kicks and punches, not Reach 2 with kicks.
So pick your poison, but I think that for clarity and game-mechanical ease, you will say that the reach of a Leg is two levels down from the Size and Speed/Range table from the basic SM, while you choose whether a punch is three or four levels down. Four will provide results consistent with RAW GURPS, three is probably more consistent with normal human limb proportions.
So if you’re (say) an SM+1 Giant Spider, the assumption will be that any “arms” you have will be the length listed for SM-3 (RAW assumption), while any Legs will be of the length listed for SM-1. That is, 1.5 yards for Legs (Reach 1), and 0.7 yards for Arms (Reach 0).
If you want longer than that, say, two-yard reach, you’ll need one level of Long Legs, and three levels of long arms. If you gave four Legs and four Arms, that’s how you’d work ’em out.
Kicking and Punching
If they manipulate, even if they can’t grasp, they’re likely Arms and will roll flat DX to strike. If they’re Legs, providing balance and motive ability, they’re probably Legs and will Kick at DX-2 and do a bit more damage (thr rather than thr-1).
Cannot Kick is a good limitation for critters that do not use their motive abilities to strike, ever.
Foot Manipulators with Ham-Fisted are a good way to represent clumsy legs that can nonetheless do some tool use and grasping, and are commonly used for this. The fact that I can pick up pencils with my toes does not give me Foot Manipulators, but if I do this, I will apply the penalties for Ham Fisted, but not give myself any points for it. Guidelines, not rules.
If I were to tweak this out, I’d rewrite it explicitly in terms of the length on the Size and Speed/Range chart, and make it two levels down for legs and three for arms. So the normal arm length is about 0.7 yards (a bit more than two feet) while a leg is 1 yard. On me, at least, that works out remarkably well.
To qualify for Reach n, you must drop fractions – so 0.5 or 0.7 is still Reach C, while 1 or 1.5 yards is Reach 1.
Then you can decide what the striking length of a particular set of limbs might be, and figure out whether from a game perspective, this is shorter or longer than the chart would indicate.