Apply Kotlin In Action practices (Elizarov, Isakova, Aigner, Jemerov, 2nd Ed). Covers Basics (Ch 1-3: functions, extensions, default args), Classes (Ch 4: sealed, data, delegation, companion objects), Lambdas (Ch 5-6: functional APIs, sequences, scope functions), Nullability (Ch 7-8: safe calls, Elvis, platform types, primitives), Conventions (Ch 9: operators, delegated properties), Higher-Order (Ch 10: inline, noinline, crossinline), Generics (Ch 11: variance, reified), Reflection (Ch 12: KClass, KProperty), DSLs (Ch 13: receivers, @DslMarker), Coroutines (Ch 14: structured concurrency, dispatchers, cancellation), Flows (Ch 15: operators, StateFlow, SharedFlow). Trigger on "Kotlin In Action", "Kotlin idiom", "Kotlin coroutine", "Kotlin flow", "Kotlin DSL", "Kotlin generics", "Kotlin null safety", "Kotlin delegation", "Kotlin inline", or "Kotlin extension".