{fancy lil calc}

src/main/java/rocks/zipcode/calcskin/CalcEngine.java

     }
 
     public double add(double v, double v1) {
-        return Double.NaN;
+       double sum =  v + v1;
+       return sum;
     }
 
     public double subtract(double v, double v1) {
-        return Double.NaN;
+        double difference = v - v1;
+        return difference;
     }
 
     public double multiply(double v, double v1) {
-        return Double.NaN;
+        double product = v * v1;
+        return product;
     }
 
     public double divide(double v, double v1) {
-        return Double.NaN;
+        double dividend = v / v1;
+        return dividend;
     }
 }

src/main/java/rocks/zipcode/calcskin/CalcSkin.java

     private VBox createLayout(TextField screen, TilePane buttons) {
         final VBox layout = new VBox(20);
         layout.setAlignment(Pos.CENTER);
-        layout.setStyle("-fx-background-color: silver; -fx-padding: 20; -fx-font-size: 20;");
+        layout.setStyle("-fx-background-color: #6c1d45; -fx-padding: 20; -fx-font-size: 20;");
         layout.getChildren().setAll(screen, buttons);
         handleAccelerators(layout);
         screen.prefWidthProperty().bind(buttons.widthProperty());
 
     private TextField createScreen() {
         final TextField screen = new TextField();
-        screen.setStyle("-fx-background-color: aquamarine;");
+        screen.setStyle("-fx-background-color: #a39382");
         screen.setAlignment(Pos.CENTER_RIGHT);
         screen.setEditable(false);
         screen.textProperty().bind(Bindings.format("%.0f", currentValue));
 
     private Button makeStandardButton(String s) {
         Button button = new Button(s);
-        button.setStyle("-fx-base: beige;");
+        button.setStyle("-fx-base: #002855");
         accelerators.put(s, button);
         button.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
         return button;
     }
 
     private void makeClearButton(Button button) {
-        button.setStyle("-fx-base: mistyrose;");
+        button.setStyle("-fx-base: #36573b");
         button.setOnAction(new EventHandler<ActionEvent>() {
             @Override
             public void handle(ActionEvent actionEvent) {