Type winter during game play to enable cheat mode. An exclamation mark will confirm correct code entry. Activate the following cheats by entering the corresponding codes. This will also unlock all buildings except for the harbor.
CHEAT FUNCTION - CHEAT CODE View entire map - ALT + F7 Change game speed - ALT + F1 to F6
If an enemy starts to build a massive military building, such as a guardhouse or better, and will easily get rid of any buildings you are constructing by occupying the building, then quickly build a barracks at the closest possible point (so that it can be occupied before the enemy building). It may be worth destroying bigger military buildings of yours so you can build the barracks. It should stop the enemy's advance. Then, destroy the barracks, and carry on as normal.
Since catapults do not cause the enemy to attack you, use this to your advantage by destroying as much of enemy land as possible without actually attacking, by building catapults. Note: Catapults use up stone supplies quickly.