header style on finish

squarenotsquare/src/screens/Game.js

@@ -88,6 +88,8 @@ function Game(props){
 
   function completeChallenge(){
     clearInterval(localTimer.current);
+    setHeaderColor(styles.darkGreen);
+    setHeaderText((Date.now() - startTime.current) / (1000) + ' s');
     setTimerState(4);
   }