CityVille's Viral Growth Hooks: Levels 1-3 Deconstructed

CityVille has grown from 0 to 90 Million Users in 30-days...insanity.

To be expected, the game is very well designed. From happy pixel citizens to cute tail-wagging dogs, CityVille keeps you emotionally glued to the screen in ways only a behavioral psychologist could understand.

For this post I've decided to deconstruct the "social sharing" of CityVille, levels 1-3. To grow their user base Zynga uses Facebook wall posts and target friend invitations through their "Goal/Reward/Share" system.

What is Goal/Reward/Share (GRS)?

Goal
Present the user with a specific goal. Example: build a house, or open a bakery.

Reward
After the user has completed the goal, present them with a reward, Example: new level achievement, more coins, or a gray bunny.

Share
This is the key to their growth, after the user receives the dopamine hit of their achievement, IMMEDIATELY present them (on the same screen) with the option to tell the world about their new found status (ego stroke) and SHARE the wealth with their friends. Remember, this is always framed as a positive thing for both you AND your friends. For example, common share button copy reads: "share the news and coins", "share XP", "share coins now", and "send gifts to friends".

In the flowchart below I've cataloged all actions that trigger a Facebook wall post or targeted invite. In a little over an hour of gameplay I was asked to share 10 times which would have resulted in 8 wall posts and 2 targeted invites (had I accepted each request).

(click flowchart to enlarge)

Further reading --
Rules of Play
The Art of Game Design