Defender's Quest (DQ) is a tower defense meets RPG hybrid. You go around with your ragtag bunch of misfit heroes, trying to save your skin and possibly the world. As you make your way, battle after battle, through hordes of zombies... I mean, Revenants, everyone's skills improve, making them harder, better, faster, stronger at slicing-and-dicing more undead meat.
Is that all? No. DQ has a delicious old-school feel, partly thanks to the pixellated sprites, partly because of the great soundtrack which will make you think of the glorious days of SNES JRPGs. It also has some notably well-written dialogue, snappy and fun (though let's face it, the art in those scenes leaves something to be desired...). DQ also has lots of challenges for you. Playing levels at regular difficulty is getting too easy? No problem, you can replay them at Advanced or Extreme to get bonuses and goodies. Finished the game? No problem, there's a New Game+ with more difficulties awaiting for you. The learning curve is extremely well-balanced and I especially enjoyed being able to complete the main story without ever getting really stuck but with a very real sense of increased hardship towards the end (the last two-three battles, especially, I barely managed to power through).
It's definitely a very good game, especially if you like tower defense. Get it.