Interesting. Any details?
Sure. I don't know if it's particularly interesting at the level of detail I can provide in a few minutes, but I don't mind sharing.
I'm writing it for my 11 year old son and his friends, which means I want it to be fast to play, easy to learn, simple in its math, forgiving to beginners, and emphasize modes of play they enjoy in their video games, like stealth and sniping. They're smart kids, but I don't see any real benefit in using the level of complexity found in many games. I also want to include meaningful mechanical athletic, chase, and investigative challenges and indulge my personal prejudices as to how a game should work.
There are character "talents" which are similar to D&D ability scores but based on what you do with them rather than personal description like "strength." They are Attack(physical), Defense(all), Perception(investigative, combat, and technical like medical), Deception (stealth, disguise, sleight of hand), Athletics, and Magic. It's a skill rather than class based game. There are no limits on what skills you can take, but the nature of the talents encourage the same type of specialization and division of labor you see in class based games.
As much as I dislike hit points, I included a similar mechanic because they make the game forgiving. To make the math fractionally quicker though, I reversed it. A PC has "health" and the player tracks "damage." If damage exceeds health they become "wounded" (you can't die from a single attack) which is pretty disabled. Further events can cause PC death.
"Control zones" in combat are pretty important. In a fight you can prevent other characters from moving through the space around you. Various mechanics are built around defeating or reinforcing this mechanic.
"Stamina" and "fatigue" work like health and damage, but fatigue is accumulated from athletic actions and special combat maneuvers. If fatigue exceeds stamina, you become "exhausted" and take a penalty on these actions and any further fatigue is counted as damage. This lets me create meaningful athletic challenges. Yes you can climb that cliff, but there are various routes, and you should make some good decisions or you're going to be too tired to use "furious attack" when you get to the top. And becoming exhausted halfway up is bad too. The penalties are bad enough that you could fall. I spent a lot of time trying to make activities like travel, swimming, and mounted combat both realistic and fun. I was surprised by how hard this was.
"Magic" and "power" work like stamina and fatigue. I'm currently working on the spell list, but spells will probably come in three flavors, those based on modern beliefs about paranormal activities, shamanistic abilities, and Avatar based elemental spells. (We all like Avatar the Last Airbender)
Actions are resolved by skill checks, talent+skill+d6+mods, with a catch-up mechanic. Any time you roll a natural 1 you get a luck point that can be added to any later roll. Defense in combat is active, with a choice of how to defend and a roll. The mods for activities like stealth can get pretty complicated to allow depth of play, but can be ignored if you're not into that.
The setting is still pretty nebulous, but I'm leaning towards combining the Powder Mage series, Wrede's Frontier Magic, Jurassic Park, and post-bioapocolypse.
I think that covers the high points. I'll probably share it here in toto someday for feedback and to see if anyone is willing to playtest it.