Machine/pro feeds from service line. Players are arranged on ad and deuce baseline across net. Players hit one approach, then two volley shots. They are trying to hit targets straight ahead/down the line at the opposite baseline. One point for balls hit just behind the service line out wide; two points for balls hit at baseline near the hash mark, and three points for any hit in the deepest wide corner where singles line and baseline intersect. See chart below for a way better explanation of the points targets.
Players rotate into opposite lines to get experience hitting from both sides of court. Player with most points at end of round wins.