diff -r 3a82f9e6eddd -r 8e31706fc5da minesweeper/src/main/java/org/apidesign/demo/minesweeper/MinesModel.java
--- a/minesweeper/src/main/java/org/apidesign/demo/minesweeper/MinesModel.java	Fri Feb 07 15:21:54 2014 +0100
+++ b/minesweeper/src/main/java/org/apidesign/demo/minesweeper/MinesModel.java	Fri Feb 07 15:40:56 2014 +0100
@@ -63,6 +63,10 @@
             }
             return "" + state.ordinal();
         }
+        
+        @ComputedProperty static String style(SquareType state) {
+            return state == null ? null : state.toString();
+        }
     }
     
     enum SquareType {