We haven’t heard much about Mozilla’s HTML5 replacement for the Flash plug-in since last year, but work on Shumway has been quietly progressing. Recently, a pair of the Foundation’s developers took to YouTube to show off what Shumway can do — and it’s pretty impressive.The video demo starts with a simple physics simulation using Box2D, and Shumway handles the falling blocks with ease. Most folks who still lean on Flash in their browser need a bit more functionality than that. Fortunately, Shumway is up to the challenge.The demo also shows Shumway running AddictingGames’ Mining Truck. It’s not the most advanced Flash game around, but it’s certainly a good test for a Flash Player replacement built using only standard Web code.But what about watching videos? Flash still dominates online streaming, so it’s imperative that Shumway be able to take over plug-in duties there, too. It doesn’t look like that task will be a problem either.Yuray Delendik’s short demo shows Firefox Nightly and Shumway playing the trailer for Man of Steel on YouTube, and it runs at least as well as YouTube’s own HTML5 player did in its early days.Clearly Mozilla has a long way to go before Shumway is ready to land in the stable version of Firefox, but the development team has made impressive progress over the past twelve months.Once Shumway is ready, Firefox users will be able to kick the Flash plug-in to the curb without missing out on all the Flash-powered content that still lingers on the Web.The best part: Mozilla’s sharing all the code as it always does, so Shumway could find its way into other browsers, too.