I'm here at Maker Faire, getting ready to demo the Popfly Game Creator, and here's a new game I just created:

You can click "tweak" to see how I created it, make changes, and save it as your own.  But here's a quick summary of what I did:

• I made the A, S, D, and F buttons by taking existing actors & changing their appearance.  (Removing the icon and adding a TextBlock.)
• I added an "Active" property to the A button initialized to 0.
• I gave the A button a constant downward motion, and set its Active property to 1 when the button collides with the horizontal bar, then reset it to 0 when it uncollides.
• I made the A button disappear when the A key is pressed AND Active=1 (using a filter on the event).
• I incremented the built-in game-level Score property by 15 when the A key is pressed AND Active=1.
• Handy shortcut: I copied the behaviors & properties on A to the S, D, and F buttons by using the "I want this actor to... act like Plus Button" shortcut.  (Plus Button is the name of the A button.  Yes, we don't support naming/renaming actors yet.  We'll be sure to add that soon!)  I then updated the references to the A key to the appropriate key.
• On the main scene, I added a behavior to deduct 5 points whenever A, S, D, or F are pressed.  (That way, the player gets 5 points deducted for an incorrect key press and 15-5=10 points added for a correct key press.)
• I added behaviors on the main scene to spawn the A, S, D, F buttons at the top of the scene, each triggered by a timer that fires randomly between 1 and 3 seconds.
• I added a scene change behavior to transition to the Won scene after 60 seconds.
• I used a timer actor that already knows how to display elapsed time, but made it count down instead by initializing its ElapsedTime property to 60 (seconds) instead of 0 and changing the code in one of its behaviors to use a - instead of a +.

Enjoy!