diff --git a/arduino/HelloWorld/HelloWorld.ino b/arduino/HelloWorld/HelloWorld.ino
index a0f2d08..2914d9b 100644
--- a/arduino/HelloWorld/HelloWorld.ino
+++ b/arduino/HelloWorld/HelloWorld.ino
@@ -1,15 +1,27 @@
 const unsigned int LED_PIN = 13;
 const unsigned int PAUSE = 500;
+const unsigned int FLASH_DURATION = 50;
 
 
 void setup() {
-    pinMode(LED_PIN, OUTPUT);
+  pinMode(LED_PIN, OUTPUT);
 }
 
 
 void loop() {
-    digitalWrite(LED_PIN, HIGH);
+  for (int i = 1; i < 4; i++) {
+    flash(i);
     delay(PAUSE);
+  }
+  delay(PAUSE);
+}
+
+
+void flash(int n) {
+  for (int i = 0; i < n; i++) {
+    digitalWrite(LED_PIN, HIGH);
+    delay(FLASH_DURATION);
     digitalWrite(LED_PIN, LOW);
-    delay(PAUSE);
+    delay(FLASH_DURATION);
+  }
 }