What is a UI case study?
A case study is an in-depth breakdown of a single project that a designer has done. A UI/UX case study can range in detail, but is commonly used to showcase the intricacies of a designer's problem solving and visual design skills. Case studies can be created as stand-alone examples or included in a portfolio.
What makes a good UX case study?
As a UX designer, your main job is to offer the why behind the designs and the product. That is why a successful case study always leverages good research, good logic, and tight-nit design reasoning. This applies to existing case studies you have done as well.