Hello,
I added virtual joysticks to my babylon-world and when I testing around with the joysticks in my iphone 6/safari the circles leave some pixels on the screen sometimes, like the "dirty rectangles" are not big enough to clean up.
Not sure if this is a safari browser bug or that you can increase the area of circles little bit to clean up better.
Also, holding the circles when tilting screen makes them stuck and you have to reload page.
kind regards
Tomas