So I have been going back and taking a look at Aftermath! as a generic system. Having over 20 years of experience with the rules makes it an easy thing, plus we learned this game when we were kids so a lot just comes naturally.
First up, why? I like the system with the hit locations, special effects, and detailed combat. This is something that GURPS sort of gives me, but there is a whole lot more work involved. Sectional armor plus hit locations is a fun minigame to play, and if you have characters with cool armor sets made of different materials and protective values you get a really interesting simulation.
Bullets and damage are fun in this game, more so than GURPS. You get all sorts of fun special effects, but simplified from something as complex as Rolemaster. Also, a d20 (roll low) dice mechanic with a heavy reliance on ability score saving throws. Damage is straightforward with special effects that cascade out from rolled-for special effects (and is also expandable easily).
The system is also very calculated and math-like, once you get through what gets added to what to fill in what spot on the character sheet you are done. All your chances of success are on your character sheet. The system plays well from character sheets, and the special cases apply equally given situation X or Y. In fact, the game comes with a handy combat flowchart so you can't really get lost on how combat works.
Golden Age Sci-Fi
I wanted to use this game for something along a golden-age sci-fi game, but more gritty and realistic. If I have advanced aliens I will just generate them as age-group 5 characters and give them a ton of skills. My rule is +5 to ability scores and 10 skill points and eliminate rolling for development and attribute points. I purposefully avoid the Operation Morpheus generation system because it is way too bloated, and 10 skill points gets me a great starting character with room to grow.
For talents I assigned the following: -2, -1, 0, 0, +1, +2, and +3 to the seven values. I didn't roll since this lets me define strengths and weaknesses my way instead of randomly. You could roll random, your choice.
So in summary 80 attribute points, 25 talent points, 10 skill points, one firearm skill, literacy (x2), tech use (x2), culture (x2), two survival skills, and brawling.
Tech Use, Culture, and Literacy are Relative
Also, keep Tech Use, High Tech Use, and Literacy relative to the cultures. Tech Use becomes Earth Tech or Space Tech, and you pick your starting culture's Tech Use skill. This makes Martians have to learn how to use telephones, while Earthlings need to figure out Martian transport tubes. High Tech Use? Well, again, culture relative if you go there and really only applicable for the "super advanced" technology of the day, such as computers in the 50's and something like technology that was lost or theoretical to the Martians.
Literacy and culture work similarly, Earth and Space, but let everyone read English and only roll for odd cases such as who Shakespeare or Guulilinak is in reference to classic literature of the planet. Culture is also similar, what is rock and roll and what is the Martian hoopa hop would be good areas for rolling.
One thing I love about Aftermath (that we knew all this time) is how remarkably flexible the game is to modify. This is a common trait to many old-school games, and I find a lot of the modern games are very easy to break and throw way out of balance. Some games exist to be completely out of balance and are further ruined by 3rd party content. The older games feel more grounded in "chance of success" and "consequences" and don't have these huge structured frameworks of class designs (that are never play tested well unless they are ancient and time-tested like B/X) bolted on them.
I can swap out the skill list. I can pare it down. I could put Gangbusters or Star Frontiers skills in there. I could do a decent Space Opera with the system. I could play fantasy. The post-apoc genre sits on the border of sci-fi and fantasy, and is grounded in modern day, so the system does everything reasonably well. I could do steampunk fine, and the whole BAP/MNA/PCA action system feels like clockwork mechanics anyways so it would thematically fit (and it isn't as complicated as I remember, just a phased initiative countdown system).
Plus you get vehicles and things that go boom. As kids, this killed D&D for us because we got to play with the big action-movie toys, real cool war stuff, and it just felt grand and epic, while being rooted in rules that were easily accessible from a single character sheet.
Simple and Fun
The system feels good to me. Likely because we used to run games that lasted years, and we played every day with a fast-and-loose version of the rules where we ignored hex maps and handled everything verbally. The characters start weak and grow to heroic proportions.
A fun system I am very comfortable using, and it feels like a great "mess around" home system with a lot of potential for random effects and outcomes in combat.
I am happy again going back, and that is something I didn't expect after spending nearly 20 years away.