Hearthstone: Heroes of Warcraft 

In this free strategy game, you are a hero that needs to battle against different enemies using a deck of cards that can cast spells, summon monsters, use weapons, and weaken the enemy's powers and defenses.

You need to play your cards wisely. Some of them can protect you against the enemy's attacks; others can invoke creatures with special powers, such as warthogs specialized in charging against the enemy; and others can cast different spells against him, such as mystical blasts, fire glows, or inflict minor damage to all the enemy's minions at the same time. There are also healing cards which allow you or your minions to recover from the enemy's attacks. Thus, you need to think fist what card to throw to make the maximum damage to the enemy and reduce the possibility of being damaged.

The game may look easy at first. In fact, the first few levels aren't too difficult to win. Nevertheless, the difficulty level increases with each new level, so the last one is almost impossible to win, thus making the game even more challenging.

The only drawbacks I found are that the installation file needs to download additional files to complete the installation, which can take a while, depending on your Internet connection speed. Also, you need to create an account and to be online to play the game. If you are a Facebook user, you can connect using your FB login information.

In sum, if you like games such as Yu Gi Oh and Sakura Card Captor, then you may enjoy this free game.