@GrahamCampbell
Finally, I'd probably be deeply remiss if I didn't point out another free option which takes elements from all of the above and puts them in a package that lets you play solo, co-op, or guided. I'm talking about #Ironsworn.
https://tomkinpress.com/pages/ironsworn
On an initial glance, you probably would say that Ironsworn has a very classical HP system just split between multiple types of impact: Health and Spirit
It is intended as a very fiction-forward game, so you are encouraged to make your decisions based on what you know of the fictive things that have happened to your character.
If you took 2 health damage and you described that as taking a shot to the arm, your fictional framing should follow suit and continue maintaining that injury within the context of your interaction until you do something to remove that injury.
However, once health or spirit get down to zero, further negative consequences have mechanical impact by imposing actual serious Conditions, Banes, and Burdens.
You can think of the counter itself as a sort of timer until narrative consequences pile up deep enough to have serious ongoing mechanical impact.
Again, you can look at this game design for free, and I definitely suggest that you do if you're thinking of doing up your own TTRPG.
#TTRPG