Canonical/common playfield-based score routines

[Nostalgic]

The canonical six-digit player-based score routine has been around for a very long time.  Is there an equivalent for a playfield-based score?  Different games had different PF score implementations.  Many early games like Combat only required two-digit scores for each player.  Canyon Bomber and Space Invaders supported two four-digit scores through leaving every other line blank.  Asteroids has a five-digit score and a life counter.  Video Pinball has an impressive six-digit score with a ball counter and player number.

 

Has a canonical or common playfield-based score routine been developed in the homebrew age?  I suspect having to deal with reversed bits in the playfield and combining two digits together info a PFx register would make it a challenge to do efficiently.

 

[KevKelley]

I had done something similar in Pinfinger but not for score but for knife position. 
 

Implementing this was easy, as I would just check some coordinate and then each number would be a line defining a couple of the playfield variables. I could picture it being easy to implement by doing something similar. 

[KevKelley]

…and what I put together wasn’t some assembly routine. Just a few lines of bB. But I imagine someone could make a kind of score routine  I wonder how Amoeba Jump made it.

[+Gemintronic]

One of my first 2600 games had two double digit scores made out of the playfield.

 

https://forums.atariage.com/topic/165874-candybar-game-for-atari-2600/