While Xbox Live games for Windows Phone 7 continue to remain online-only affairs, that hasn’t stopped indie developers from creating games with online play. Lately we saw Broiled Earth, a competitive artillery game, and now thanks to Haypi Kingdom, Microsoft’s mobile platform has its first MMO (Massively-Multiplayer Online game).

The game's description, according to Haypi Kingdom’s official website:

Haypi Kingdom is a massively multiplayer online role-playing game (MMORPG). You will be a general directing an ancient kingdom in a strategic game - boosting resource production, adventuring in extensive wild land, reaping legendary treasures, equipping your troops with advanced abilities and fighting against enemies - with the ultimate goal of becoming the strongest kingdom in the ancient world. Your general can get higher title and more advanced attributes as he joins more and more battles. His attributes will be shared among his troops as well.

You won't play alone. In this massive multiplayer online game you will be able to interact with thousands of players from all over the world in a competition for fame, power, wealth and glory. What's more, there are plenty of possibilities to interact with others - Not only offense and defense, but also trade, alliance, mail system, chat system, etc.

Of special note is Haypi Kingdom’s revenue model. The game is free to play, but players can purchase in-game coins through optional microtransactions.

Coins can be used to speed up upgrades, enhance resource production, buy VIP time to add upgrading slots, buy resource or treasures, call back troops, and enhance your city loyalty immediately, etc. Coins can only [be] purchased with real money at "SHOP". Each player is awarded 30 coins when they first play the game.

Basically, coins allow impatient players to speed up various processes in the game. Smurf Village on iPhone and of course Farmville use similar payment models.

We previously heard from another developer that microtransactions were prohibited on Microsoft's mobile platform, so it’s surprising to see that may not be the case. Micro payments would certainly open up the door for more popular online games to come to WP7.

Gamers who are interested in a social role-playing experience on Windows Phone 7 can get Haypi Kingdom for free here (opens a link to your Zune software) on the Marketplace. We’ll have a full review of the game soon.