What criteria should meet the flash-game on the site?

I decided to make a flash game for the site

Purpose:
- creating entertainment content
- website promotion through viral marketing
But the question arose
What criteria should a flash game have?


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After analyzing how sites promote themselves through games.

For example, on the portal of Ekaterinburg about active recreation they made a flash-game Ural fishing
On the site Be Happy Toy Court offended women
On the site Business Quarter game management decision generator

Came to conclusions
1. The game must match the content of the site.
2. There must be a clear idea in the game.
3. The game should be interesting.
4. Link to the game should be easy to remember.

What do you think? Are there among you those who were engaged in the creation and development of entertainment content on thematic sites?
What is the effect of the organization?