Just when you'd warmed to the idea of three navigation buttons on HTC's One lineup, the company went back and re-added a fourth button to the row -- in mainland China, anyway. To follow the debut of its Desire (aka Dragon) lineup, HTC has introduced a One S variant that it designed in collaboration with Sina Weibo, the country's most popular alternative to Twitter. The phone sports a dedicated Sina microblog button, along with a set of bundled software from the popular weibo service, but otherwise remains true to its namesake. The handset will be available in both black and gunmetal blue enclosures, and will sell for 4,688 yuan, or approximately $740. Our associates at Engadget China recently snagged a hands-on with HTC's latest, and have provided a video tour for English audiences to enjoy. Take a peek after the break.