LAUSANNE            -            Roger Federer delighted fans by posting a video on Twitter on Tuesday, which shows him executing some trademark trick shots against a wall in the snow. The 20-times Grand Slam champion last played at the semi-finals of the Australian Open, where he lost to eventual champion Novak Djokovic, before undergoing keyhole surgery on his knee in February. He is supposed to return to playing in time for the grasscourt season in June. “Making sure I still remember how to hit trick shots #TennisAtHome,” Federer tweeted along with the video, which showed the Swiss moving around seamlessly amid snowfall.