Good Game.
You can see the improvements that have been made over other versions, but I agree the strategy is too easy (buy archers, you don't even need cannons). This game is pretty good, but things that could improve this game would be as follows: 1. balancing the use of all the units(infantry, archers, ect.), you could do that by making the castle change up its attack over time, so it forces the player to change up his/her own tactics. 2. It would be helpful to know if upgrading the units is doing something, honestly I can't tell if its doing anything.
Otherwise this is a pretty solid game, I did enjoy tinkering with all of the units (although it gave me minimal success) Also I did enjoy the improved graphics of the game. It should would be cool to see another version of this game.