I am pretty bad at using JavaScript so I wish to add a health counter to my game. Does anyone have a code that would work with Squiffy? Other codes I've looked into seem as if they won't work. I'm confident with using HTML and CSS.

I just do @set health = x for my health. it seems to work just as good unless you need more complex code for some reason.

After you set health, you can change the value by:
@dec Health x
or
@inc Health x

Just make sure you spell Health the same way as you did in @set Health = x