RP6
Really¸ most TTRPG rules boil down to "I can do this if the GM says I can." We have certain bits set down as rules¸ so it's an inviolable right that you can add your Strength modifier to Strength rolls when you're playing D&D¸ but there's equally enough GM fiat and jiggery-pokery behind the scenes that setting the Target Number higher can completely negate that modifier. The dice sit in the middle as a charming arbitrator¸ and to remove some of the perceived responsibility from the GM¸ but they're in charge and you're gambolling for their favour.
Anyway¸ to grossly oversimplify it: all roleplaying games are bullshit and are an exercise in framing fictional concerns modulated through the prism of social interaction between players and GM. So when I was writing the simplest possible one¸ I wanted to say the quiet part out loud and condense almost all the rules into "convince the GM that it's a good idea." RP6 is that.
It's pretty much the purest form of roleplaying you can have¸ and everything else we do as games designers is guide rails that push the story¸ tone¸ pacing etc. in different directions. (Not that "pure" implies "best¸" here. Unprocessed sugar cane is all well and good but I can't make a cake with it¸ can I?)