Cortex Prime. Extremely hackable, nearly impossible to break. Powerful to reinforce flavor with mechanics (which is what I think you're going after). Simple mechanics (if you don't go ham with the Mods).
Mark of the Odd games (Into the Odd, Mausritter, Into the Bronze, etc.). Extremely fast character creation, the rules so light they're almost not there, very few rolls, very deadly rolls.
The font and color scheme are very much on point. Traditionally fuel would be marked, but everyone knows all the nooks available are used for fuel, so I don't mind the omission.
They are very strict on what sort of content goes there, though.