reveal lost iPhone 4 safari compatibility

[camic]

Hello
I think reveal.js lost iPhone 4 safari browser compatibility after upgrade to latest reveal.js
It used to work before the upgrade. I do not remember which version it was before, but it had a lib/ folder. and it worked.
I do not know the safari browser version that is inside the iPhone 4.
I would like to know if there is a desire in reveal.js to maintain backward compatibility with old browsers.
To test, simply try to run reveal.html ( that is the one with two slides )

Slide 1

Slide 2

it shows a black screen under safari on an iPhone 4.
I am looking for a workaround.
thanks for listening.