He wears a funny mask with a smiley face on it. The mask is in the shape of a cylinder (圆筒). And the eyes on its face look like multiplication signs (乘号). He is US DJ Marshmello, 26, whose real name is Christopher Comstock. He has created many popular songs. One of them is called Happier. He worked on the song with British pop band Bastille and released it on Aug 17 this year. It reached No 2 on the UK Singles Chart (排行榜) and No 3 on the Billboard Hot 100, becoming Marshmello’s highest-charting single. It sounds quite cheerful.