val frente a var: inmutabilidad desde el primer día

val name = "Kotlin"
println(name)
// name = "Java" // Error: Val cannot be reassigned

var counter = 0
counter = 1
counter += 1
println(counter) // 2

val age = 25          // inferred: Int
val name: String = "Ana"  // explicit type
var score: Double = 0.0

val list = mutableListOf(1, 2, 3)
list.add(4)        // OK! list is val but mutable
// list = mutableListOf() // Error: reassignment

val pi = 3.14159     // constant value
val greeting = "Hi"  // never changes
var retries = 3      // will be decremented

const val MAX_SIZE = 100    // compile-time
val instance = MyClass()    // runtime

var result: String
result = "computed"
println(result)

val x = 10
run {
    val x = 20  // shadows outer x
    println(x)  // 20
}
println(x)      // 10

val firstName = "Jane"     // camelCase
const val MAX_ITEMS = 50   // UPPER_SNAKE_CASE
class UserProfile           // PascalCase