I stumbled upon a very interesting game about 2 weeks ago and I've fallen in love with it.
In Pokemon Tower Defense, you start the game like you would with any other Pokemon game; choose which version you're playing (Red or Blue) and choose a starter Pokemon (Either Bulbasaur, Charmander, or Squirtle).
The gameplay is very similar to other tower defense games at first. The Pokemon serve as your towers and you can place them in certain designated spots.
However, this is where the cool stuff comes in. Each Pokemon, like in the actual game series, has a move set of up to 4 moves. Charmander, for example, starts with Scratch and Growl. You can use these moves to either hurt or harm your opponent's status. With each hit, you gain money (whatever they call the currency in Pokemon) and EXP. You level up your Pokemon and they can evolve through gameplay!
Plus, if you manage to get a wild Pokemon's health into the red (low health), then you can hold the Pokeball icon, drag it over to the weakened Pokemon, and catch it. Now, that Pokemon is in your party and serves as a new tower to use!
The game is still being made, and is constantly updated with new levels, Pokemon, and challenges being added. Make sure to try it out and give some feedback!
Pokemon Tower Defense!