The article explores the design of LEGO interface panels and how they can teach us about physical interface design. It breaks down the problem of designing complex machine interfaces into two key questions: differentiating between the function of different inputs and organizing the many inputs and outputs. The article analyzes various LEGO panels and identifies different approaches to organization, including feature-based, operation-based, and technology-based. It also discusses the importance of shape coding, color coding, and other methods for differentiating between inputs.