5 Fists is a coin-based mini rpg.
It's a couple pages long, split across a few different pamphlets. The core rules fit on a single page---although you do have to rotate the PDF to read them---and the fonts are very readable.
Mechanically, things are pretty simple. You flip a coin for skill checks. If you have an advantage, you flip two coins. One heads is a success. Double heads is a crit. You don't take damage, but failing to stop an incoming attack can take you out of a fight until you get healed. There's also an elemental weakness system where different characters have different elemental affinities that can give them bonus coins when they clash.
That all said, some of these rules do require a bit of interpreting. It's not clear in the text whether heads and tails cancel each other out, how you know which character has which elemental affinity, and what inspiration coins are.
For GM resources, there's a story seed that sets the stage for an initial encounter, but it's very open-ended and you'll need to fill in a lot of the context yourself. There's also some recommendations for safety tools.
Overall, if you're looking for a very lightweight, martial arts flavored trpg system, 5 Fists is worth a look. You'll need to do some legwork in setting up the scenario and interpreting the rules, but this is also a game that you can read once and then be able to run it without ever looking at the book again. As long as you have a few coins in your pocket, it might be perfect for car rides, camping trips, and other situations where you want to play something quick without books or other equipment.