Looks and works great! Your launch timing was perfect—Mirr.io outshines InVision’s Craft Prototype plugin in almost every way.
My only feature request other than additional transitions, would be to provide an iOS and Android native app that would enable you to hide the OS status bar and view prototypes with the status bar shown (or not shown) in the Sketch artboards.
One bug — if I set a timer on the very first artboard in the prototype, it doesn’t seem to work in the web browser version of the prototype.
Keep up the great work. Looking forward to where you take Mirr.io.