@Canageek you might look at the classic Marvel Heroes system for inspiration. that's also percentile. I also used to play Harn Master ages ago, which was percentile as well. There's plenty of places to draw from!

@geekalogian Yeah, I've got the core of the game done, at least in draft. The hard part is adding the magic system and balancing it. I can see how I want everything to work in play, but there isn't really any way to get a magic system to balance with fighting without lots of playtesting.

@Canageek That's an issue in a lot of systems. I recall the magic system in HarnMaster being interesting, but incredibly tedious. A lot of it is so dependent on setting, too.

@geekalogian Yeah, really trying for setting-free. I'm going to start with a list based on old D&D spells from early on, but add in some d20 Modern stuff to make sure it looks generic enough.

@geekalogian The core is magic is just a skill, roll under your skill to cast spell. Each one reduces your skill until you rest though, so it gets harder to cast spells as the day goes on. Plus, more powerful spells penalize your skill to cast, and take more points off the top when you do cast them.

I say theoretically as I got the basic mechanics done, and then stalled out when I started on magic. I've got notes written into a notebook, and lots of editing comments on paper, but haven't sat down at home to type them up.

@Canageek
Magic is always fun to design in a world. Since designing a system you are essentially bringing about the laws of physics that exist in the universe your players will inhabit, its part world-building part number crunching nightmare. XD

@BeCeejed Mostly number crunching nightmare as it is a generic system. I'm sure there is a way to figure out optimal amount of damage to have spells do vs weapon attacks, but not sure how to go about it....

@Canageek
Well your weapon attacks can pretty much be done as often as you want provided you are still standing, so the total life damage of a weapon attack is (individual damage x average rounds before being incapacitated per long rest/healing/reset)

Magic on the other hand is usually limited to a certain expenditure of points, be it spell slots or some sort of mana pool. So there are less total instances of magic use per weapon attack use.

@BeCeejed Right, so first I have to determine how many weapon hits I want a PC to be able to take. Then work out how many spell hits I want them to be able to take, and I can scale from there, I guess.

But how do I work out stuff like, say, Shape Stone: lets you reshape 1 m^3 of stone?

@Canageek

@Canageek
You're basically looking to balance your Total Magic Damage per Reset with your Total Weapon Damage per Reset, by adjusting the average damage per spell and the size of the mana pool.

That's how I always viewed spell slots in DnD anyways spells do more damage but you do less of them, tends to balance out tho. This doesn't really account for spells that provide buffs, debuffs, or problem solving workarounds, like Shape Stone, as you suggest.

@Canageek
I would say you do one of two things: 1) Utility Spells draw from a different pool. Lots of utility spells are cantrips, for instance, and don't cause loss of spell slots.

2) You increase the pool to slightly larger than it needs to be for a perfect Magic Damage/Melee Damage ratio. Most spellcasters have at least a few utility spells they use, so in actual play it tends to balance out, but gives them the option to be DPS MVP with careful strategy.

@BeCeejed Ohhh, 1) is a good idea. I was going to do thematic spell groups, but splitting them up by type actually is more true to my vision, as it encourages use of utility spells.

There was a great point when 4e came out that no one will EVER cast Mount. Great spell, useful, but it is 3rd level. You know what else is 3rd level? Fireball, lightning bolt, haste, dispel magic. You might as well not even HAVE other 3rd level spells with those 4 there.

@BeCeejed But if I have by what they do, instead of a more flavourful class, that bypasses the whole issue.

So spell skills
Attack Spells
Buff/Debuff Spells
Utility Spells
Healing Spells.

@Canageek
If that's the path you go down, also think melee vs Magic in skills usage. If melee build characters have less utility, because they don't have skills that do what casters can do, they should definitely have a larger Total Damage Per Reset than spellcasters, because spellcasters get to shine in more scenarios. Or, spellcaster builds get debuffs for other skill checks maybe.

@BeCeejed Skill based game, so the penalty for spellcasters is they can't pick up other useful skills. So your non-casters will be better diplomats, rogues, etc.

@Canageek
Ah, so like Shadowrun, then? I've only played D&D, Pathfinder, Shadowrun, and Star Wars Edge of the Empire. More Shadowrun than any of them I'm guessing.

@BeCeejed Yeah, except it discourages overspecialization. Magic is just a skill, and armour doesn't hurt it (currently), so fighters could take a few points in it so they can light their swords on fire or such, or rogues could learn some darkness spells.