diff --git a/2025/01/kotlin_demo1/README.md b/2025/01/kotlin_demo1/README.md
new file mode 100644
index 0000000..5bcd79d
--- /dev/null
+++ b/2025/01/kotlin_demo1/README.md
@@ -0,0 +1,3 @@
+# Basic kotlin project
+
+The goal was to test how easy / hard is to write kotlin in vim :-).
diff --git a/2025/01/kotlin_demo1/build.gradle b/2025/01/kotlin_demo1/build.gradle
index cd4ea39..0c0fd16 100644
--- a/2025/01/kotlin_demo1/build.gradle
+++ b/2025/01/kotlin_demo1/build.gradle
@@ -12,5 +12,5 @@ kotlin {
 
 tasks.register('runApp', JavaExec) {
   classpath = sourceSets.main.runtimeClasspath
-  mainClass = "ProgramKt"
+  mainClass = "pl.polgrabia.demos.kotlin.ProgramKt"
 }
diff --git a/2025/01/kotlin_demo1/src/main/kotlin/Program.kt b/2025/01/kotlin_demo1/src/main/kotlin/Program.kt
deleted file mode 100644
index 81cfcd8..0000000
--- a/2025/01/kotlin_demo1/src/main/kotlin/Program.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-fun main() {
-  println("Hello World!!!")
-}
diff --git a/2025/01/kotlin_demo1/src/main/kotlin/pl/polgrabia/demos/kotlin/Program.kt b/2025/01/kotlin_demo1/src/main/kotlin/pl/polgrabia/demos/kotlin/Program.kt
new file mode 100644
index 0000000..48aef6e
--- /dev/null
+++ b/2025/01/kotlin_demo1/src/main/kotlin/pl/polgrabia/demos/kotlin/Program.kt
@@ -0,0 +1,12 @@
+package pl.polgrabia.demos.kotlin
+
+import kotlin.collections.*
+
+fun main() {
+  // val data = listOf(1, 2, 3, 4)
+  val data : Array<Int> = Array(10) { 1 }
+  val s = data.reduceOrNull ({ r,v -> 
+    r + v
+  })
+  println("Hello World!!! Sum: $s")
+}