A kaleidoscope built using (almost) pure CSS3

Here's a kaleidoscope made using pure CSS3. Ok, almost pure CSS.
The only bit of JavaScript is used to kick off the animations. I could have done this is CSS too, but ran out of time.
The way it works is there's a 500px square div containing a triangular -webkit-mask-image (defined by the SVG file). This mask image ensures that regardless of the size and position of the background image, you only ever see a triangular shaped section. You can think of it as a 'cutout'.
This div is duplicated, flipped and rotated eight times to create the effect. We then animate the resulting 'scope by simply moving the position of the background image.
I think it's quite neat. Unfortunately this fairly simple page actually crashes iPad and iPhone devices running (at least) 5.1.1 after a while. Very frustrating!

View Demo

Source Code