SpectromancerSpectromancer is a fun little game made by Richard Garfield, the creator of magic. It follows similar rules, but the joy of it is in the tactical elements, rather than desk building. Indeed, your deck is randomly chosen for you at the start of each game. Each level provides a different challenege, which steadily increases as the game goes on. The AI can be fiendish, and on some of the harder scenarios, probably impossible to beat when you get bad luck in the combination of cards you are provided with. I don't know how well balanced the game is- it seems like some cards are just strictly better than others, but mostly it works well.
The demo is rather extensive, and if you've ever enjoyed magic I guarentee you will enjoy this.