Improvements based on user feedback

Today we released the first update to our game based on user feedback.

• The objective of the level is described in the splash screen shown before the level.
• The progress indicator (the white cube that is spawning when you place bricks) now shows how many you have placed out of a total (eg "4/6" instead of just "4" which was confusing to users). You also get a clearer indication by this cube when you have dropped enough bricks.
• Added a pulsing effect to the brick before it is dropped.