In a hotel lobby on Hong Kong Island, a delivery robot pauses outside one of the lifts as the doors open, and a guest steps out. The robot waits, and then rolls neatly inside. The move looks simple, but it isn't. To work in the busy hotel, owned by an international chain, the robot must navigate a building that won't slow down for it. People are often getting in the way, and it must be able to take the lift to the correct floor, and then find the right room. The company behind the robot, Yunji,