Mockup design techniques, a core practice within Human-Computer Interaction (HCI), involve creating static, high-fidelity visual representations of a digital product's user interface. Unlike lower-fidelity wireframes, mockups meticulously detail the visual design elements—including color schemes, typography, spacing, and imagery—to present a realistic preview of the final product using tools like Figma, Sketch, or Adobe XD. This critical step allows designers, developers, and stakeholders to evaluate and iterate on the interface's aesthetics and usability before committing to development, ultimately serving as a precise visual blueprint that guides front-end engineers during the software implementation phase.