Outward Bounders

So I had this idea a while ago of a sort of reality-hopping campaign. Rather than consecutive scenarios taking place in a continuous world, the PCs would regularly slip into different universes (or planes, or dimensions). This would certainly offer aesthetic changes, as well as changes in the availability of technology, magic and other resources; how much it would change the tone and genre I'd have to see.

I see this as something where the PCs would not be in control of their journeys. They might end up shifting inexplicably, either through some kind of affliction, or under the control of higher authorities (be that government agencies or warring deities). Alternatively, it might be some kind of meandering quest: perhaps they're travelling through a series of unmapped portals, trying to get home, or to reach some other destination. Homeward Bounders is probably my main inspiration here, though things like Mighty Max and even The Wishing-Chair share some of the same ideas.

That doesn't necessarily mean the players don't have any control. A DM with fantastic ideas and a great knowledge of what would suit the group might be able to repeatedly conjure up amazing new worlds for them to adventure in, but it's probably best to do some negotiation with the players to see what sort of places they'd like to visit. It's also going to depend how people see the campaign. A serious dimension-hopping storyline, probably with some kind of genuine plot arc going on, facing the gritty reality of adjusting to alien lifeforms and massive swings in technological ability, is going to be a very different kettle of fish from a madcap journey through Robot Dragon World and the Elemental Plane of Sweets.

Switching to different realities would mean different resources become available to the PCs. In some places magic might be non-existent, but in others, you can't get away from the stuff. Some dimensions might offer fabulously advanced technology that makes our most brilliant scientific advances look like the wheel, while others think the wheel is a brilliant scientific advance. I sort of imagine the PCs accumulating motley abilities as they pass through different realities, though not all would always be viable, or indeed safe. You might end up with a solar-power robot arm, four healing spells, a bottled ghost pirate, and expert knowledge of interstellar navigation and flint-knapping. But try explaining the robot arm to a mediaeval mob. Again, a very down-to-earth campaign might tackle the practicalities and problems of augmetics or magic in other dimensions, while a pulpy one might handwave anything that wasn't cool.

What system?

To handle something like this, there's basically three options. One is to switch to an appropriate system for each hop, which would mean trying to recreate characters in multiple systems (a time-consuming process, with translation loss and gain every time), getting used to new systems regularly, and working out how adapt items, creatures or abilities appropriately if we want to be able to accumulate cool stuff during the campaign.

Yeah, that sounds like a right barrel of laughs.

A second option would be to pick a single system that people enjoy and are comfortable with, and then basically stick with it regardless. Problems would be hacked or handwaved by the GM. No rules for cybernetic implants in your AD&D rules? Treat it like a magic item. No rules for horrific Lovecraftian magic in your Traveller books? Graft some on, or make a ruling on the fly. You want to stuff Wyle E. Coyote's ghost into a Dalek shell and feed him telepathic instructions to hack the Death Star from the inside, in your Hellcats & Hockeysticks game? ...actually, that one probably works.

On the whole, though, that strikes me as a decent basis for a campaign that happens to veer into unexpected territory, but not a good starting point for one that plans to be esoteric and hotchpotch from the outset. You're just asking for trouble, and rulings you make early on could easily come back to bite you in the posterior.

The third, and I imagine the best, is to start from the outset with an adaptable system that can accommodate a variety of settings, and hopefully genres. Obviously any system is going to suit some things better than others, but something designed for generic gaming will probably do better than a niche game. On the downside, those kinds of systems will lack the depth and richness of more specific systems that focus on particular elements of the game, or on particular tones and genres.

Generics

The main generics that I'm aware of are GURPS, BRP and of course, D20. In some ways I'm most tempted by the D20 option, probably because I'm most familiar with it. On the downside, it's quite a fiddly system in some ways, and takes a while to get used to if you aren't. Also, spellcasters are utterly OP after a few levels. On the upside, the fiddliness allows a lot of scope for flavour, genre evocation and creating mechanical differences. It has detailed rules for casting arcane spells, for performing combat manoeuvres, for cybernetic implants and for starship combat. You can temporarily allow or disallow particular classes, spell types, technologies and abilities to reflect character background or dimensional variation. You can vary the background magic level, the abilities granted by different deities. There's a whole array of playable species, many with special feats available reflecting their racial capabilities, like extra-scaly skin or unusually sharp teeth. You can mix classes, allowing characters to gain levels appropriate to the current setting.

On the other hand, a much looser system might be better for a handwavy romp through space and time. In something like BRP, you can just establish some skills and use them for pretty much everything. New and unexpected challenge from a bizarre universe? Invent a new skill. There's simple mechanics for acquiring and improving skills based on use. It's really pretty quick and simple to use. There's bolt-on options for fairies, morris dancing, robotics and superpowers. A downside of the system's simplicity is that signature abilities and tactics are largely non-existent, with differences between characters largely down to skill percentages. This could end up making what should be the cool weirdness of (say) acquiring robot arms or learning from octopus martial artists, into just a few numbers.

Outward Bounders

It was originally just a silly title for this post, but I've actually got quite tempted by the idea of an Outward Bounders setup. If you're not familiar with Outward Bound, it's one of these outdoor education schemes for young people. They encourage hiking, camping, boating, and that sort of thing. One possibility for a campaign would be to have an organisation that encouraged even more exotic sorts of exploring and independence, sending people off on inter-reality journeys. Portal-hopping could work a bit like orienteering, so they have to collect proof of reaching their various destinations before they can return. If their home culture is sufficiently macho or psychotic, then sending them into quite dangerous journeys would be fine - the same's true to some extent if they're part of some tough organisation.

Coming at it from another angle, maybe the Outward Bounders are - like most kids sent on these things - unwilling participants, perhaps suddenly thrust into adventure by some extradimensional authority that selected them as suitable victims subjects candidates for this ordeal highly advantageous, character-building leadership programme. Which makes perfect sense to them, but not to the motley band they've imposed this on. Maybe they're all plucked from different worlds (might be fun), with no way home until they complete the programme. Some might relish it, others hate the whole business.

I'm still not sure what kind of tone I'd like - I think you could get about as much mileage out of this by treating it either as a fun romp, a fairly serious fantastical adventure, or a deadly serious straight-faced game of really ridiculous things happening. I mean, the prospect of humourless Dimension Ranger recruits trekking through a planet of Blytonesque talking animals, being press-ganged into a terrifying school and battling their way out of a chocolate prison (and then moving on to a serious Asimovesque robot planet or the Forgotten Realms) really appeals to me.

Anyway, as with most of my ideas I suspect nothing will come of it. But it's a nice thought.

First impressions of AD&D 2nd Edition

So my Wednesday night group is just starting our new VOIP game, which will see Arthur unleashing us on a lovingly-crafted Advanced Dungeons & Dragons Second Edition game. This is actually my first time playing anything earlier than 3rd, outside of Baldur's Gate and the like. I do have a broad idea of how things work - I think I first encountered the rules in a copy of Dungeon bought to placate me on a family visit to relatives in New Jersey, of all things - but I don't have the kind of familiarity I'd like. On the plus side, it's a very knowledgeable group of people who are very good at explaining things.

Our first session was just getting things ready. We're using a new bit of software for VOIP, so had to play with settings and features a bit, and there's a new player that I hadn't met previously. Mostly though, it was chargen.

I read through the Player's Handbook last week to brush up on things, though quite soon it turned into skipping. A lot of the information there is pretty specific, and I don't really need to memorise lists of spells and equipment, or alternative ways of doing non-combat stuff. That's all nice to know, but it wasn't really worth poring over before the game's even started. Anyway, here's my first impressions of the game.

Obligatory THAC0 bit

THAC0, on reflection, doesn't seem as bad as it's often suggested to be. It's not very intuitive, and certainly compared to the simplicity of a Base Attack Bonus (which works in exactly the same way as every other modifier to your die roll) it's arcane. Having both THAC0 and Armour Class start high and improve as they decrease, in contrast to every other part of the game and most aspects of real life, displays a piece of logic that I find completely baffling. I can't imagine any reason why anyone would ever, ever choose to use THAC0 when other options were available.

That being said, I think some of the problem stems from a needlessly confusing explanation. Here's the game's description of THAC0 in use:

The first step in making an attack roll is to find the number needed to hit the target. Subtract the Armor Class of the target from the attacker's THAC0. (Remember that if the Armor Class is a negative number, you add it to the attacker's THAC0.) The character has to roll the resulting number, or higher, on 1d20 to hit the target.

Rath has reached 7th level as a fighter. His THAC0 is 14 (found on Table 53), meaning he needs to roll a 14 or better to hit a character or creature of Armor Class 0. In combat, Rath, attacking an orc wearing chainmail armor (AC 6), needs to roll an 8 (14-6=8) to hit the orc. An 8 or higher on 1d20 will hit the orc. If Rath hits, he rolls the appropriate dice (see Table 44) to determine how much damage he inflicts.

Now what if we imagine the same rules, explained by someone sober?

Roll a d20 and add the target's Armour Class. If you equal or exceed your THAC0, you hit.

Rath has reached 7th level as a fighter. His THAC0 is 14 (found on Table 53). In combat, Rath, attacking an orc wearing chainmail armour (AC 6), needs to roll an 8 (8+6=14) to hit the orc. If Rath hits, he rolls the appropriate dice (see Table 44) to determine how much damage he inflicts.

But it's still not fantastic. So what's THAC0 doing wrong? Well, a mixture of practical and descriptive issues, I think (and bear in mind this is mostly theoretical, partly based on Actual Play podcasts, and with a smattering of Baldur's Gate, rather than direct experience of the tabletop game).

• You need to know the enemy's AC, which the DM must tell you each time, giving away useful information (and reducing any possibility of constructive fudging).
• It requires subtraction, which people tend to find slower than addition - especially when negative armour class comes into play.
• Amour class starts high, then decreases as it improves. Chainmail has AC6, but magic chainmail +1 has AC5, not AC7. Not only is this unintuitive, it's effectively contradicting itself. I can see where they were coming from (pluses are good, minuses are bad) but anytime you can avoid having to memorise arbitrary system-specific exceptions to normal use, you should.
• Under the suggested description, you reverse any bonuses, deducting positive numbers from your THAC0, and adding the value of negative ones.
• Similarly, a dagger +1 gives a bonus that must be subtracted from THAC0, not added to it.
• You're expected to calculate THAC0 for each specific weapon you have, each of which must then be modified to fit the target.
• THAC0 itself is, a lot of the time, a sort of secondary statistical entity, at least one step removed from anything concrete: it's the number you must roll to hit an Armour Class of 0, which you are virtually never doing. This makes it fiddlier to think about, in much the same way that standard deviations or a chi-squared x² value are slipperier to think about than arithmetic. A Base Attack Bonus is a number you add to your die roll; a Bend Bars percentage is the percentage chance you have to bend some bars. These are much more intuitive.

As far as I can see, the switch from THAC0 to Base Attack Bonus must be one of the most sensible decisions in gaming history, at least in terms of making the game accessible.

Layout

The layout also suffers from some organisational issues. Most notably, it's quite hard to actually get all the character information beforehand. Saving throws are under the section on combat, not in character generation - in fact there's no real character generation section. Now, in fairness, they may have deliberately decided it wasn't necessary. For example, you may not strictly need to know your character's saving throws until you encounter the appropriate hazard. However, I did find it very disconcerting sitting with a character sheet, flicking back and forth as I tried to work out where the missing information was. I'm used to systems with a fairly all-encompassing chargen, where you can start at the beginning, fill in your sheet as you go, and then be ready to play. In contrast, AD&D seems almost to leave things so that you only work them out as necessary, which in some ways makes it quite like a Bethesda RPG. I'm not prepared to say that it's objectively a bad thing to do; I'm not remotely qualified. What I can say is that it leaves the game relatively difficult to absorb before you start play; and that that seems likely to cause delays when those rules do eventually come into effect.

Another issue is, the book points you towards specific chapters for things, but only displays chapter numbers on the first page of each chapter. Instead, it offers cutesy symbols on the remaining page: crossed swords are combat, a hand is wizarding, a hand with an ankh is priesting, a random assortment of objects that looks like something off a white elephant stall is class descriptions, a troll snarling in your face is encounters... There are two major problems with this approach. The first is that some of them really aren't very intuitive, but the names of the chapters are given alongside them if you open the pages properly. More pressingly, this in no way helps with the lack of numbers, since finding Combat or NPCs is no flipping use to you in finding Chapter 5: Proficiencies unless you also know what number every other chapter is. Yes, there is an index, and a contents section, but it's much nicer to just be able to flip through the book. This is particularly true when some chapters are only two pages long, and can be pretty tough to find. So, could do better.

I also found the presentation of options in some places cluttered and confusion - for example, there are different ways of calculating effects of encumbrance, and I spent quite a while trying to work out how they fitted together, before eventually spotting that they are alternatives rather than complimentary systems. The table for basic encumbrance doesn't mention movement at all, but is followed on the next page by a table listing detailed movement penalties for encumbrance. As I was trying to fill in a character sheet, I just worked through them. It's only on the third page - after descriptions of animal carrying capacities, stowage for containers, mount encumbrance and magic armour - they they get around to explaining how the basic encumbrance rules work with movement, at which point I very slowly realised something was up. But look, if you have a table called "Modified Movement Rates" that lists how encumbrance affects your movement, I don't think it's that unreasonable to assume that the latter is what you use. Stick an "optional" in the title or something, don't explain that bit in a sidebar that isn't even adjacent to it.

In terms of the burning question "is this laid out less usefully than Call of Cthulhu (6th edition)?", I'm yet to reach a final verdict. I suspect it's going to be a close call.

Saving Graces

The saving throws are really very arbitrary, and read almost exactly like "stuff what's come up in games I ran so far", rather than any kind of systematic attempt to create a system for avoiding effects. There's the random list of quite specific magical effects, with their own little subsystem, but then any other possible effect is just an ability roll. I have to wonder why it didn't occur to them to try and mesh the two.

There's a weak argument you could make based on the text in the book, which for the Everything Else saves says: "When a character attempts to avoid danger through the use of one of his abilities...", implying that the set saves cover passive resistance and everything else is an ability roll. But that's a bit misleading, since it should be possible to actively avoid quite a few breath weapons and some kinds of spell - anything from fireballs to hypnotic gazes to visible tendrils of transmuting energy. While I can see how you might evolve a system of level-based saves for miscellaneous effects, why split them down in this way? Why are Poison, Death and Paralyzation one save, and Petrification another? Why are Wands and Rods different from spells cast any other way, and why are both different from Poison anyway? Why are Warriors more vulnerable to Poison than Rogues are, and why are Wizards better at surviving Breath Weapons than anyone else?

Yeah, I'm not convinced.

Fast, Short and Lively

On the upside, I was pretty impressed with the speed of basic character creation. Filling in the sheet took quite a while as I rummaged through the book in search of saving throws, equipment weights or whatever. However, actually rolling up Oswyn was really simple. Six lots of die rolls, followed by a fairly simple choice of class: generally you won't be qualified for about half the classes as they have ability prerequisites, and if you have one or two high scores you really want to pick the matching class.

As it happened I had generally decent scores, but high Strength and Con, so a fighter was the obvious way to go. Also, to be fair, I wanted something straightforward for my first game in the system. Having picked a fighter, all there was to do was pick a couple of weapon specialisations and go shopping. No skill points to carefully apportion, with an eye on feat choices a few levels later. No feats to choose. Admittedly I actually rather like feats, but that's not the point: they do add another, really quite large, layer of complexity. Also, in fairness, we aren't using weapon proficiencies (only specialisations) nor non-weapon proficiencies, which does save some time. And we're aiming for a human-based campaign. We did roll up backgrounds to help with character inspiration, though. But yes, I was impressed than in about an hour and a half, we managed to test the VOIP software, introduce ourselves as necessary, establish some background, create characters, shop, start working out party backstory and do a fair bit of nattering.

So far, my time breakdown looks pretty much like this (in order of time spent, not in chronological order, in case you're really confused by my apparently bizarre approach to chargen):

1. Fill in character sheet: ~30 mins
   1. of which ransacking rulebook: ~ 24 mins
   2. of which entering information: ~5 mins
   3. of which arithmetic: ~ 1 min
2. Choose name: ~10 mins
3. Invent character: ~5 mins
4. Pick class and character abilities: ~2 mins
5. Roll attributes: ~1 min
6. Pick class: ~30 secs
7. Pick race: ~1 sec

whereas a typical Pathfinder breakdown might look more like:

1. Pick class and character abilities: ~30 mins
1. of which reading feat descriptions, synergies and prerequisites: ~25 mins
2. Choose name: ~10 mins
3. Pick class: ~2 mins
4. Fill in character sheet: ~5 min
1. of which entering information: ~3 mins
2. of which ransacking rulebook: ~ 1 min
3. of which arithmetic: ~ 1 min
5. Invent character: ~5 mins
6. Pick race: ~1 min
7. Roll attributes: ~1 min

Finale

So on the whole, I've got some reservations about the actual product. That doesn't really affect my anticipation for the game: as I said, I've got an experienced DM, everyone else has solid prior experience with the game, and I don't really expect to run into any problems. So I'm pretty excited.

And obviously, this is an early RPG, and it's not entirely fair to compare it to more recent developments and try to draw some kind of direct equivalence between them. Later editions of D&D, and pretty much everything else, have... well, at least had the opportunity to learn from AD&D 2nd edition, both in terms of actual rules, system coherence, and also fluffier issues of layout and organisation.

So yes, a not particularly deep non-review of a twenty-year-old RPG system. Woot. I can't imagine why this blog hasn't acquired a fanatical cult following yet.

Inspirations: the Sands of Time, part five

A while ago I started looking at whether you could take anything interesting from Prince of Persia: The Sands of Time for use in RPGs. I've had a quick overview of general ideas and issues, and then considered how you might handle things in Pathfinder or BRP. I've also looked at the combat system in detail, and considered how it might be converted for tabletop.

Homebrew

For the sake of interest, I'm going to consider an entirely new mechanism. We want PCs to successfully fight against multiple opponents; in POPSOT, the PC attacks faster and more accurately than the monsters, and is better at defending.

The Necromunda and old Warhammer 40,000 combat system appeals to me for this. For each opponent, you both roll d6s equal to your Attack score, add your Weapon Skill and any modifiers (such as terrain or multiple attackers), and the difference in scores is the number of hits taken by the loser. A more skillful fighter will typically win a fight without a scratch, as their high Weapon Skill gives a higher final figure. A fast-striking fighter can overwhelm an opponent, because they roll more attack dice and have more chance of getting an optimal roll. A single fighter can fight multiple opponents, rather than having to pick one to fight while the others attack freely. A skillful fighter can defeat multiple opponents without automatically being overwhelmed, because each fight is largely independent; but statistically, fighting several opponents is still more dangerous, because there are more chances for a poor die roll to scupper you.

As I'm aiming for a fairly streamlined system, I'm looking at something inspired by this, but reducing its complexity somewhat. Here, you'd simply roll opposed dice, but different creatures would have different die sizes. A PC might have a d8 compared to a normal enemy's d4, for example. Weak enemies have small dice, and powerful enemies have large dice. What would that look like?

Crunching dice

With a PC d10 versus an NPC d4, the PC will win 30/40 combats. With a PC d8 versus an NPC d4, the PC will win 22/32 combats. With a PC d6 versus an NPC d4, the PC will win 14/24 combats.

Matrix of possible results

Die size	PC die			d3	d4		d6		d8		d10		d12
Enemy die		1	2	3	4	5	6	7	8	9	10	11	12
	1	-----	1	2	3	4	5	6	7	8	9	10	11
	2	LOSE	-----	1	2	3	4	5	6	7	8	9	10
d3	3	LOSE	LOSE	-----	1	2	3	4	5	6	7	8	9
d4	4	LOSE	LOSE	LOSE	-----	1	2	3	4	5	6	7	8
	5	LOSE	LOSE	LOSE	LOSE	-----	1	2	3	4	5	6	7
d6	6	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1	2	3	4	5	6
	7	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1	2	3	4	5
d8	8	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1	2	3	4
	9	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1	2	3
d10	10	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1	2
	11	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----	1
d12	12	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	LOSE	-----

Proportion of PC wins

Die size	d3	d4	d6	d8	d10	d12
d3	1/3	1/2	1/3	3/16	2/15	5/48
d4	1/4	3/8	7/12	11/16	3/4	19/24
d6	1/6	1/4	5/12	9/16	13/20	17/24
d8	1/8	3/16	5/16	7/16	11/20	5/8
d10	1/10	3/20	1/4	7/20	9/20	13/24
d12	1/12	1/8	5/24	7/24	3/8	11/24

For multiple opponents, each combat could be rolled separately, or PCs could roll one die per opponent and then allocate them against the enemy results. The second would give them a significant advantage, since the combat system already favours the PC, allocation reduces randomness, and randomness favours the underdog. I think this might be too strong as the standard mechanic, and I also suspect it would make combat against multiple opponents actually easier than against one.

Sequential versus allocated rolling in mass combat

Logically, let's say an enemy can only beat you on opposed d6s if it rolls a 6 and you roll a 1. This will happen, on average, one out of 36 times. If you fight two opponents in succession, by rolling separately for each opponent, the chance of you losing at least one fight is...

At this point, I realise I've forgotten nearly all the statistical knowledge that I painstakingly absorbed at school. I spend some time researching probability distributions.

Okay. The other version is easier. If you win unless you roll a 1 while they roll a 6, your probability of victory is 35/36. If you fight two opponents and roll separately for each, the probability of you winning both is 35/36 x 35/36. This makes 1225/1296, or 0.95. The probability of losing one or more fights is 0.05, or about 5%. For three opponents, the probability of flawless victory is 42875/46656, or 92%, while there's an 8% chance of you losing at least one.

Next, you fight two enemies using the roll allocation mechanic. If the enemies roll 5 & 6, and you roll 1 & 2, you simply allocate your 1 against the 5, and your 2 against the 6, countering both hits. The only way for you to either combat is if either both roll a 6 and you roll at least one 1, or if you roll two 1s and they roll at least one 6.

Wow, my maths is somewhat rusty, but that actually looks like a much nastier calculation than I initially thought... I'm sure there probably is a nice, statistical way to manage that, probably using Poisson distributions and factorials, but I'll stick to basics.

They roll two 6s and you roll one 1: 1/36 x 10/36
or
They roll one 6 and you roll two 1s: 10/6 x 1/36
or
They roll two 6s and you roll two 1s: 1/36 x 1/36

10/1296 + 10/1296 + 1/1296 = 21/1296
= 7/432
= 0.016

If my maths is accurate (a dubious thing), the chance of you taking at least one hit in a fight against two opponents is only 1.6%. What about three opponents?

They roll three 6s. You roll a 1. (1/216 x 25/216) - three arrangements
+
They roll three 6s. You roll two 1s. (1/216 x 5/216) - three arrangements
+
They roll three 6s. You roll three 1s. (1/216 x 1/216) - one arrangement
+
They roll two 6s. You roll two 1s. (5/216 x 5/216) - nine arrangements
+
They roll two 6s. You roll three 1s. (5/216 x 1/216) - three arrangements
+
They roll one 6. You roll three 1s. (25/216 x 1/216) - three arrangements

Multiplying all the possible arrangements of all the possible combinations gives a probability of 406/46656, or 0.009ish. This means that in combat against three opponents, the chance of you taking one or more hits is a mere 0.9%.

Under sequential rolling, you have a 3% chance of injury when facing one opponent, a 5% when facing two, and an 8% when facing three. These figures are, however, exactly the same as if you fight three enemies one after the other.

Under allocated rolling, you still have a 3% chance of injury when facing one opponent. Against two, that drops to only 1.6%. Against three, it's down again to 0.9%. Combat gets easier the more enemies you're facing! While this might be a nice mechanic in some situations - for example, if you're going for a comedy tone where the clever PCs can make opponents get in each other's way - it's not really appropriate for this one. Too much Law of Ninja for my taste.

Sorry about that. Probably my longest tangent ever, but I'm not going back to check.

So yeah, as I thought, sequential rolling for the win. I'd probably give a small modifier for each subsequent opponent, just so there's some advantage in numbers.

Combat Options

Defensive fighting might let shrink your die size. For every size you drop, you can parry two hits you would otherwise take from each opponent you face. Is this worth it?

If you're fighting an opponent with d8, and you have a d8, on mean you'll take zero hits. However, you can take anywhere up to 7 hits if you roll badly. One to four hits is relatively likely (mode 1, standard deviation 3.5). A PC in bad shape, or who has a lot of opponents to fend off without much support, may not be able to take that. By dropping a die size to d6, you slightly increase the number of hits you're likely to take (and significantly reduce your chance of scoring any hits yourself), but can ignore two of them: the likely pool of damage increases from about 3 to about 4, but two are ignored, giving a slight defensive bonus. Dropping even further, to a d4, means you could readily take up to 5 hits, but can parry four of them. A d3 allows up to six parries, at which point it's very difficult to damage you at all. While I don't claim to be mathematical expert, it looks to me like this mechanism would actually do what's intended.

versus d12	d8	d6	d4	d3
MEAN	-2.18182	-3.27273	-4.36364	-4.90909
STD	4.305958	3.940111	3.615798	3.476381
Parry	0	2	4	6
RESULT	-6.48778	-5.21284	-3.97943	-2.38547
versus d8	d8	d6	d4	d3
MEAN	0	-1.14286	-2.28571	-2.85714
STD	3.495452	3.064919	2.650746	2.455315
Parry	0	2	4	6
RESULT	-3.49545	-2.20778	-0.93646	0.687542
versus d6	d8	d6	d4	d3
MEAN	0.571429	0	-1.2	-1.8
STD	3.064919	2.690981	2.23842	2.00713
Parry	0	2	4	6
RESULT	-2.49349	-0.69098	0.56158	2.19287

There could also be a reckless fighting stance, which gives you more hits but makes you more likely to take damage yourself. I'm not quite sure how to do this, as simply increasing the die size just makes you more likely to win the combat, without risk. A slightly complex option would be to grant an increased die size, but to calculate enemy hits with a penalty, perhaps half the number rolled. For example, you might upgrade to a d10 and roll a 7, which compared to the enemy 5 grants two hits. However, for defensive purposes it only counts as a 4, and so you also take a hit.

This system doesn't immediately lend itself to any kind of active defence, which is a slight downside. It ought to allow fairly fast and simple combat, though. But if we're looking for something more tactical, I'm not sure this would be great - it might actually be better to have a more complex system if combat is going to be a major aspect of the game, just as D&D fleshes out things significantly. While I could go with a Necromunda-style system of simple modifiers to die rolls, it's just not very interesting for an RPG, however well it works in a tactical miniatures game.

This system also has the downside that it's a homebrew. Which means I'd still have to establish systems for handling everything other than combat, and it's probably riddled with flaws. So to be honest I'm probably better off sticking with something established. Still, I had fun.