The Journal’s Mike Shields reports that Yahoo’s proprietary ad-buying platform, Yahoo Gemini, is starting to turn heads. Yahoo has been beefing up its targeting capabilities since debuting Gemini in February and hopes its focus on mobile will help its solution standout. Cadreon Global President Arun Kumar, for one, thinks Gemini is promising. “I think this is Yahoo’s big play,” he said. “It’s picking up quite well in the market.” The challenge for Yahoo now will be to build awareness among big marketers and agencies and integrate the offering fully into BrightRoll, the digital video ad tech firm Yahoo snapped up in November.