Finishing the Penguin Pairs Game - Building JavaScript Games for Phones, Tablets, and Desktop - page 301

In order to temporarily display the arrow, you reuse the VisibilityTimer class from the Jewel Jam
game. You create an instance of this class and add it to the game world as well:

this.hintVisible = new VisibilityTimer(hint);
playingField.add(this.hintVisible);

You also add a button that the player can click to display the hint on the screen:

this.hintButton = new powerupjs.Button(sprites.button_hint, ID.layer_overlays);
this.hintButton.position = new powerupjs.Vector2(916, 20);
this.add(this.hintButton);

Finally, you extend the handleInput method of Level to deal with the Hint button being pressed:

if (this.hintButton.pressed)
this.hintVisible.startVisible();

The Hint button can only be pressed if it's visible, which in some cases it shouldn't be:

 After the player makes the first move, the Hint button should disappear, and the

Retry button should appear.

 If the player chose to switch off hints in the Options menu, the Hint button

should never be visible.

For the first case, you need to keep track of when the player makes their first move. You add an
extra member variable firstMoveMade to the Level class. When you give an animal a velocity, this is
done in the AnimalSelector class. Once the player has clicked an arrow and the animal is moving,
you set the firstMoveMade variable to true :

this.selectedAnimal.velocity = animalVelocity;
this.root.firstMoveMade = true;

Second, you have to handle the Hints setting from the game Options menu. You do this in the update
method of the Level class. You simply check what the value of the Hints setting is in the GameSettings
variable, and update the Hint and Retry button visibility state accordingly:

this.hintButton.visible = GameSettings.hints && !this.firstMoveMade;
this.retryButton.visible = !this.hintButton.visible;

As you can see from these two lines of code, the Hint button is visible only if GameSettings.hints is
true and the player has not yet made a first move. The Retry button's visibility status is always the
opposite of the hint button's visibility status. So if the Hint button is visible, the Retry button isn't,
and vice versa.

Resetting the Level
After a player moves a couple of animals around, it can happen that the level can't be solved
anymore. Instead of having to quit and restart the game, let's give the player a means to reset a level
to its initial state.