1. A method comprising: displaying a first timeline for a first animation object; displaying a second timeline for a second animation object; displaying a first identifier of the first animation object in association with the first timeline; displaying a second identifier of the second animation object in association with the second timeline; wherein the first identifier and the second identifier are displayed with respect to each other in an order that determines a z-index order of the first animation object with respect to the second animation object in a style sheet animation of at least the first animation object and the second animation object; generating style sheet language text which, when processed by a style sheet animation processor, causes the first animation object and the second animation object to be animated in the style sheet animation in accordance with the determined z-index order; wherein the method is performed by a computing device.