Kotlin language and standard library reference.
Kotlin lists, sets, maps, and sequences — creating, iterating, and transforming
Kotlin coroutines, suspend functions, and structured concurrency — async programming the Kotlin way
Kotlin's delegation patterns — class delegation, property delegation, lazy, observable, and custom delegates
Kotlin's null safety system — nullable types, safe calls, elvis operator, and common patterns
Kotlin's type system — data classes, sealed classes, enums, inline/value classes, generics, and type inference