Acidosis

A young man lies on his side, propped up on a pillow, holding a smartphone in front of his face with his right hand, using the front-facing camera to take a selfie. He smiles and makes a peace sign with his left hand, which is visible in the phone's screen, while his head rests on his left hand. The phone screen shows a live view of his face and the gesture, and the image on the screen briefly flickers and changes as he moves slightly. The background is a plain, light-colored wall.