Intraclass Correlation Coefficient (ICC) Design, Calculation and Interactive 'shiny' Toolkit // A comprehensive toolkit for intraclass correlation coefficient (ICC) analysis, integrating three core functionalities: (1) Closed-form sample size calculation for ICC estimation with assurance probability, based on Zou (2012) doi:10.1002/sim.5466; (2) Full implementation of all 10 ICC types (6 common + 4 supplementary) for point estimation, exact confidence interval calculation, and formal hypothesis testing, following the methods of McGraw Wong (1996) doi:10.1037/1082-989X.1.1.30 and the standard decision framework; (3) An interactive 'shiny' application that guides users through ICC type selection, performs calculations, and provides reliability evaluation based on the Koo Li (2016) doi:10.1016/j.jcm.2016.02.012 criteria. Compared to existing packages, it provides a unified decision workflow and supports all less common ICC variants.