In general we created a system that affords to manage pages states, their appearance and disappearance in range from 0 to 100%, moreover, these ranges could overlap and create kind of step-by-step timeline and parallel animation: simultaneous transition from page and to another one. System allows transitions to both directions back/ forward and opening of page using direct URL (History API).
We realized great number of complex effects and mechanics: animated circle masks, 3d sticking and mouse tracking, frame-by-frame SVG animations, zoom slider and many-many other curious. Actually we implemented flexible system of state control and management of source loading.