Animating with Code
After exploring a few routes (like SVG animation) I ended up using GreenSock's animation library to animate the coloured circles. For the circular screen-wipe transition at the end of the animation, I used vanilla JavaScript with HTML5's Canvas to achieve the desired result.
Their idea with this was that everyday on your first visit to ITV's website, they'll overlay their usual website and show you this fun little animation which disappears after it's played and won't be showed to you again for the rest of that day.
