A method of updating virtual worlds based on interactions between real-world items is disclosed. An interaction between a first real-world item and a second real-world item is detected. The first real-world item is a real-world item that is associated with a first player of a computer-implemented game and the second real-world item is a real-world item that is associated with a second player of the computer-implemented game. A virtual world of the computer-implemented game is updated based on the detection of the interaction.