diff -r 2e3945ff7b66 -r 832d1e5d601b progs/cube.scala
--- a/progs/cube.scala	Thu Dec 11 13:23:30 2025 +0000
+++ b/progs/cube.scala	Mon Dec 15 18:42:41 2025 +0000
@@ -26,13 +26,15 @@
 }
 
 
-abstract class Colour
-case object White extends Colour
-case object Yellow extends Colour
-case object Orange extends Colour
-case object Red extends Colour
-case object Green extends Colour
-case object Blue extends Colour
+enum Colour {
+  case White 
+  case Yellow
+  case Orange
+  case Red 
+  case Green
+  case Blue
+}
+import Colour._
 
 // Faces
 //    -------
@@ -102,7 +104,8 @@
          Face(c.f1.c11, c.f1.c12, c.f6.c21, c.f6.c22))         
 
 
-// simple bf-search without generating a solution, just true
+// simple bf-search without generating a 
+// solution, just true in case there is a solution
 
 def actions(c: Cube) : List[Cube] = 
   List(up(c), clock(c), right(c))