Last night, I watched a History Channel show about battles in the Old Testament. Most of it was your usual "Billobab smote Jehosameme," and "Lo, did many chariots rumble." Amid all the smiting, inspiration struck.
During one of the Philistine invasions of the Jezreel Valley, it was noted that the Israelites wore leather armour while the Philistines wore heavier scale, which hampered their mobility in the mud of one particular battlefield. Saul and Friends won the day.
So I'm thinking, "How would I recreate that in Chimera?" And the answer smote me.
Dead Bird 1: Attack TNs
In the example above, terrain was a factor, but more importantly, it's a precedent for how a lack of mobility makes for an easier target. For whatever reason, the slower you are, the easier you are to hit.
Since shifting the Target Number model in Chimera a few weeks ago, I've wrestled a bit with the TN requirements for a successful hit. My original logic was to base it on defender size, such that bigger targets were easier to hit. But that doesn't quite sit well with me—for the average character, it made hitting goblins really hard and hitting giants or dragons really easy. While armour still absorbed damage, tipping the hit probability scales this way didn't feel right.
Thanks to the Philistines, I think the answer is: attack TN equals the defender's current Movement Rate (MR).
The fact that it's hard to hit fast things seems to be minimised in a lot of RPGs. Concomitantly, a combatant's speed rarely seems to be a factor during a fight (outside of how many squares on the battlemat each mini can cover).
Here's how it works: Billobab has MR 12". That means an attacker hits on a d20 roll of 12 or more. Now let's say Billobab wear mail and is laden with stuff so that his Encumbrance is 3, making his movement 9". Now an attacker needs a 9 or more on the d20. In other words, encumbrance not only affects your movement rate, but how easily you're hit.
Note that armour is still "ablative" in the sense that it absorbs damage. But with this change, lightly armoured targets are harder to hit, though they take more damage when they are. Conversely, it becomes easier to hit heavily armoured opponents, but damage will be lower. Parry and cover are unchanged (i.e., they add to the attack TN but have no effect on damage taken).
Dead Bird 2: Size and Movement
The only problem with using MR as an attack TN is that in Chimera, base movement is a function of creature size, so that the bigger a creature is, the higher its Movement Rate. My design logic (since version 1.x) is that big creatures take bigger steps and therefore cover more ground per round. This means that for big beasties with high MRs, you'd have crazy high attack TNs.
But I gotta admit: I've never completely embraced the bigger-equals-faster generalisation. A big, fat dinosaur might just lumber along, while a little, bitty housecat is pretty quick on its feet. However, I can easily rationalise separating the two: First, combat movement is more of a tactical thing, so in a fight, big fat dinosaurs cover just as much ground each round as a human-sized opponent. I mean, Cloverfield Beast was HUGE, and the little army dudes ran circles around him. Second, I don't recall a correlation between size and movement rate in pretty much any other RPG (cf. D&D B/X, where each character or beast—regardless of size—has one of essentially 5 or 6 movement rates: 30', 60', 90', 120', 150', or 180').
By "normalising" movement rates and decoupling from creature size, it doesn't seem like I'm breaking any major expectations or well-established conventions. Put another way, I can adjust movement to suit my other needs.
Dead Bird 3: Movement Rates
And while we're on the subject of movement, let's discuss crawling and running. In Chimera, MR represents walking—how many 10' blocks you can cover at walking speed. Crawling or creeping is half one's current Movement Rate while running is double. Easy enough, but if I'm using MR to indicate attack TN, then characters will be come invulnerable simply by running around (i.e., if Billobab has MR 9", I need an 18 to hit him while he's running).
So part of this exercise is figuring out how to make movement realistic without making combat too hard (or too easy). As I recall, Savage Worlds uses a die roll to indicate running speed, which is an interesting possibility. So how about this:
When you creep around, you still move at half your MR. But when you run, you roll a die and add the result to your MR—the result is how much you can run that round. This lets you reflect fast creatures (or beasts what can sprint) without giving them ridiculously high Movement Rates—just give them higher running dice than normal. For example, a human might get 1d6, while a horse gets 1d10.
Putting It Together
Let's say a human's base MR is 12"+1d6. This means that, unencumbered, he moves 12" per round. He can creep or crawl at 6" per round. When running, he adds 1d6 to 12 each round (i.e., he runs between 13" and 18" per round). Let's also say a goblin's MR is 12"+1d4—he crawls at 6" per round and runs between 13" and 16" per round.
The human is wearing mail (Enc 2; DF +2), carrying a shield (Enc 1, Parry +1), a broad sword (Enc 1) and gear (Enc 1). His total Encumbrance is 5, reducing his actual MR to 7"+1d6. Now he crawls at 3", walks at 7", and runs between 8" and 13". When attacked; these values represent the Target Numbers required to hit him, depending on what movement mode he's using (hint: don't get caught crawling). However, because he has a shield, attack TNs are increased by +1. If he is hit, his mail reduces damage by 2.
The goblin is wearing leather (Enc 1, DF +1) and carrying a short sword (Enc 0). His total Encumbrance is 1, reducing his MR to 11"+1d4. You can do the math to figure out different movement modes, but it's easy to see that his lack of encumbrance makes him harder to hit during a fight, but not at the expense of an outlandish MR, tons of armour, or size-based assignments. Plus, when he is hit, his lighter armour will let more damage through.
OK, that's a lot to digest—pretty much a late-afternoon mind dump of a thought I've had for only 16 hours and no doubt has holes.
But I think this has serious merit, and I'm going to test it out. Thoughts appreciated—have at it.