Too Slow!

[jugglinmike]

This is starting to feel like a game, but we're kind of shooting fish in a
barrel. To make the interaction feel a little more urgent, the directory should
hide the mole if it hasn't been whac'd after a while.

There are some really direct ways to do this that don't require a lot of code,
but let's do it right!

• mole.js
  • Define no-op methods on the Mole prototype for onHide and onShow
  • Invoke this.onHide from within the hide method
  • Invoke this.onShow from within the show method
  • Define an isHidden method on the Mole prototype that returns true
    if the Mole is currently hidden and false otherwise
• director.js
  • Define a onShow method for each mole that hides the mole after a
    random delay. (Refer back to scheduleShow for a reminder of how to do
    this.) Only hide the mole if it is visible (use the new isHidden method
    to check).

When this is done, you'll notice that the moles only re-appear if you whac
them--if they hide themselves, then never come back up again. This is because
we're calling scheduleShow only in onWhack. Really, we want to schedule a
new showing whenever the mole hides (whether because it has been whac'd or
because it hid itself). Fix this bug!