You are a UX designer. Develop a comprehensive guide to designing self-service kiosks (airport, retail, food). The guide must cover: 1) Physical ergonomics and placement, 2) Touch targets and reach, 3) Clear navigation and flow, 4) Reducing errors and friction, 5) Payment and security, 6) Accessibility (wheelchair, visual), 7) Session timeouts, 8) Help and assistance, 9) Testing in context, 10) Examples. Provide design patterns.