diff --git a/csharp/Controller.cs b/csharp/Controller.cs
new file mode 100644
index 0000000..ecd8b77
--- /dev/null
+++ b/csharp/Controller.cs
@@ -0,0 +1,6 @@
+public class Controller {
+    public int SelectMode(int sensor) {
+        if (sensor > 80) return 2;
+        return 1;
+    }
+}