Nice game...needs work though
It's definitly much more fun to attack a castle than to defend one. Fun it was but i think you should put in one last effort. Basically it just needs a few more inhancements and controls. I'd like to be able to stop my units after i've deployed them for one thing or maybe even order a retreat. It would also be nice to have the ability of selling back after buying (for a lower price of course). Also, surviving units left over on the battle feild should carry over to the next round (i'm fairly sure that soldiers don't commit suicide after a victory). Now, about the upgrades...they didn't seem to have any noticable effect. I'm asuming that they effected offense but i'd like them to effect defence as well. Last but not least, add music. Music really adds to the overall feel of game.
Other than all of that...nice game.