You know how to use Kotlin, but do you know the advanced features? What are the consequences of using variance modifiers? What limitations do they introduce, and how can these be overcome? How does property delegation work? How to use reflection? How to implement a KSP or an annotation processor? How is a Kotlin Compiler Plugin implemented? If you want to know the answers to these questions, this book is for you. This book focuses on the advanced aspects of Kotlin's development. These are often features and tools that developers use daily, even though they dont know exactly how they work. This book explains them and gives you the knowledge to use these features in your projects. WHO IS THIS BOOK FOR? This book is for developers with Kotlin experience who want to learn about its advanced features. Readers are expected to have experience in Kotlin development. All the required knowledge can be discovered in the books Kotlin Essentials and Functional Kotlin. WHAT IS COVERED? This book focuses on advanced Kotlin features, including: Generic variance modifiers Interface and property delegation Kotlin Contracts Kotlin and Java interoperability Multiplatform development Using Kotlin/JS Kotlin reflection Annotation Processor Kotlin Symbol Processor Kotlin Compiler Plugins Static Analysis with custom rules