Heh, forgot about that. It uses the 
View Transition API and conveniently, you can enable it with a bit of CSS. 
@Jeremy P made me aware of it and I quite liked the effect.
You can do the same by sticking this in to your style's extra.less template:
	
	
	
		Code:
	
	
		@media not (prefers-reduced-motion)
{
    @view-transition
    {
        navigation: auto;
    }
}
	 
 
There's more details 
here and it's possible to customise the transitions further but that's not something I've looked in to much.
Unfortunately, 
it's also not supported by Firefox yet which is what I use and why I forgot that I had added it.