I think if it is just a single atack level, you should make it a SIEGE level. The only thing I should do was to move my archers and than wait until enemy break the walls and than use my horses. Nuthin else. Really. You gave me the possibility of placin pitch, but it was useless, because I didnt have a stockpile, neither a pitch. And what about caged war dogz, killin pits or boilin oil? Or at least some kind of spearmen militia. I was thinkin bout 2.
I could only do it on easy. There is no way: really no way you can do it on normal. I give you one good advice: TRY TO PLAY EVERY LEVEL YOU CREATE. Otherwise it will end up like tis. Mebbe if you would add some more crossbowmen or decrease the number of enemy.
Like I said: This should be a siege level, cuz itz too short. Well, you wrote I must defend my castle against wolfs men and they must seize those 4 squares before they can get in the castle. But truth was, that they can seize just one, than pull down the gate and it is over.
Map design: 2/3
Nature:1, castle 3. The nature was there, but you just quickly scuffled it. There was a marsh, stone and metal. But it looked like it was transported there by a convoy of trucks. Also the dirt: I doubt, you did more than two clicks with the mouse. If you build a castle, please, build it in the line of the game cells (squares) - aslant. When you build it like you did (across), it is hard to place my men on the walls. If you do it like I wrote, maybe you can also place stairs on the map and it wouldnt look bad.