Alright, I've got a basic concept for a game here. Half-Tone Halcyons is built around a sort of classic superhero roleplaying format.
I'm using my Initiated SRD, which is a lightweight d100 core that can be expanded fairly easily.
The core of Initiated is that each character has Attributes and Specializations, which they add up to get a Target Number.
Roll beneath the Target Number and you succeed. Drop the ones-place digit. What you have left is your Margin, which gives a boost to whatever you were trying to do.
To build on the core, Half-Tone Halcyons has an archetype system, powers, and gadgets.
Attributes are universal and shared between all characters, making them the fundamental lever that the game rules operate on.
Specializations reflect learned and practiced abilities or unusual physical characteristics.
Archetypes give a "party role" to a character (e.g. DPS, support, tank, skills). Each archetype is associated with an attribute (though this is more of a correlation than a causation).
Powers are your usual buffet list of abilities, with the option to pick from them for points. Most have to be activated with Energy.
Gadgets function kind of like Things in the Initiated SRD. They may provide a bonus to TN and/or Margin, and the Gadgeteer archetype can add special abilities on their own (and, with the right development options, their allies') gadgets.
Attributes
Attributes are a scaling system. A character picks one attribute for their Prime Attribute and two Secondary Attributes. The Primary Attribute rating ranges from 20-35, depending on the mood of the game (street-level to world-wide). Their Prime Attribute has the full rating, while their Secondary Attributes have a -5 penalty and unchosen attributes are at a -10 penalty (this saves on bookkeeping, but also means that the "level" mechanic is the GM increasing the Prime Attribute value). There's no hard cap on Attributes, but the GM determines their advancement.
Strength, archetype Bruiser.
Quickness, archetype Speedster.
Toughness, archetype Survivor.
Awareness, archetype Sleuth (pending new name?)
Intellect, archetype Gadgeteer.
Charm, archetype Leader.
Specializations
Specializations are a second layer of character-specific abilities. You never need a Specialization, but since the d100 system tends to make you fail pretty often without a bunch of bonus modifiers on the raw Attribute number, it helps to have one. These are narrative and take the form of "I can" statements. (e.g. "I can fight," or "I can fly.")
Players and GMs agree on these statements before play, and they can be nudged and tweaked; we explicitly suggest "I can VERB" style statements, and then anything after that is details ("I can fly because I levitate" or "I can fly with my wings" both have the same mechanical effect, but may have some extra narrative outcomes).
Usually a Specialization runs from 5-15 at character creation, and they cap around 30.
Archetypes
Archetypes include a free ability and an ability a character can add.
Each archetype will have a handful of selection picks for Constant Powers, including the Enhanced Attribute ability, letting them use a superpower for free instead of expending Energy on them, and a discount on certain powers.
Bruisers can improvise throwing weapons for ranged combat and get a minimum bonus damage (stacks with Powers/Gadgets). They don't have as much of an discount list (single-target powers), but make up for it because they have a stacking bonus.
Speedsters move between combat ranges without needing to spend an action on it. They get discounts on expensive multi-attack powers.
Survivors recover from Setbacks more often. They get discounts on additional resistance and regeneration powers.
Sleuths get an Intuition ability that lets them ask the GM questions. They get discounts on unnatural senses and reroll abilities (and maybe something with doubles results?).
Gadgeteers can exchange superpower points for Gadgets that ignore the usual limitations. This replaces their power choices, though they get special options for customizing their Gadgets (like Remote Activation).
Leaders can share Energy with their fellow heroes. They receive discounts on energy management abilities and party buffs.
I'm not opposed to adding more, I just want to limit the scope off the bat. Archetypes don't give number bonuses, just a special ability.
Powers
Powers are the unique element for Half-Tone Halcyons that defy anything I've done so far in my system. There's a loose parallel in unique talents, but Powers work a little differently.
One Power that is relatively novel is the Enhanced Attribute power, which each archetype gets for their favored attribute. This gives a +1 Margin on all tests using an attribute, making successes more powerful (may also apply a modifier, not sure how I feel about that given that many characters will have Enhanced Attribute permanently on). These will also have narrative effects (e.g. Enhanced Strength means you can lift 800 pounds beyond what you'd lift normally for each point).
Some powers will scale (Enhanced Attribute, for instance). Others will be one-off.
Using a power requires Energy, unless you've paid extra to unlock it as a Constant Power.
Superpower Points are a currency that, like the Prime Attribute, are determined at the start of play by the GM's chosen power level. Unlike the Prime Attribute, they are bought with XP (which goes into a pool for Archetype upgrades, Powers, Specializations, and Gadgets.
Gadgets
Gadgets are items that each have their own uses (as opposed to the Energy pool, though Gadgeteers can convert Energy to device uses). These are mostly number-pushers, though the Gadgeteer may buy special abilities for their gadgets.
Combat
Combat is abstract, with a sector-based movement. Each Margin on a player's attack does Setbacks to enemies. Enemies attack against a player's defense (all rolls are player-centered), and players attempt to remove Setbacks based on their incoming effects.
Technically, you can use this ruleset for social combat, but I don't think I'm going to. Bad guys, secret identities, and the like might be beyond scope for the project.
Setbacks
Instead of a vanilla-style health system, characters suffer "Setbacks."
These include:
Injuries (self explanatory)
Confusion (hinders most actions)
Publicity (reveals Alter Ego, which might have mechanics if I get time, also hurts social rolls because it's always "negative" from the villain)
There are also narrative setbacks, which are anything the GM wants to impose. If you've fallen in the river on a winter day, you get the Wet & Cold setback and it hurts your Toughness tests to stay warm, but it might not hinder anything else.
A Setback imposes a -5 penalty on relevant tests. If the penalties from Setbacks exceeds a character's Prime Attribute, they're incapacitated.
Goals & Timeline
My goal is to let players simulate pretty much any superhero while staying in the "any player with experience won't be overwhelmed and you can probably introduce 12+ kids to roleplaying with this" difficulty range.
With Attributes, Specializations, and Gadgets (both Specializations and Gadgets can represent magic or other superpowered stuff that doesn't fit neatly in the Powers section), I think you're pretty much a go on the more modest characters, and the Powers and Archetypes give a more superheroic element to things.
In the past I've used the predecessor of this system with just Attributes, Specializations, a more advanced but unnecessarily bulky gear syste, and generic low-power talents that superpowers are replacing, to run or play everything from Arabian Nights to giant robot battles to weird fantasy, so I think this should be doable from the gameplay side.
The two concerns are balance (everyone should feel useful, I'm not so concerned with 1:1 power) and accessibility (keeping it easy to play).
I'm giving myself three days. I'm doing a daily game project for the month of May, and I've already done my game for today, will do a microgame for tomorrow, and will make this my sole focus on Monday. I'm recycling directly from my Initiated SRD and my other similar games.
I already have about 2000 words of what will probably be 10-15k words in the Half-Tone Halcyons rulebook, and my focus for the rest of the night will be to borrow components from other Initiated-compatible rulesets to get my combat and other stuff in place.