An animation where the start and end blend seamlessly together to create the illusion of a never-ending animation with no beginning or end. Note that an obvious fade between the start and end, or a fade to black/white are not seamless transitions.
Examples
post #2126657 - A looping animation because the start and the end of the animation are identical.
post #2083043 - Not a looping animation because it has a distinct beginning and end.
