Epic defense Battles is a strategy game with 3 different classes to choose from, loads of upgrades to buy, achievements to unlock and enemies to kill. If you have't played it yet, you can play it here
There are many strategies with which you can win the game in each and every mode. However there are few elements that are common in all of them. Like getting the first gold for kill upgrade would be a good start. However Bounty Hunters class gets that upgrade for free. So each class is equipped with its own set of advantages and disadvantages. If you choose rangers, go for first gold for kill upgrade and then first window upgrade to place more archers as archers are strong in this class. Moreover their upgrades are cheaper as well as the archer costs less to make. So, there is no reason for one to not to make archers after choosing rangers. The combination of archer and spearmen is considered very good as it can take care of enemy knights which archers find difficult to kill. Its also fun to play with swordsmen and archers, but gets a little trickier and requires some extra skill to handle knights. If you take riders, they have very effective and cheap knights including cheaper upgrades and first knight upgrade is given for free for them. However to win using riders, you should upgrade knights or atleast get gold for kill upgrades. Doing both side by side is a good strat and with that you can handle any set of army units.

To Clear hard and insane modes, follow the following tips:-
1) Get the first gold for kill upgrade as soon as you can. Also to use powers like freeze more effectively, use it when you have placed a bunch of units on the ground, enemy is near to your units and some of your units have already seen the enemies. This will buy you some extra gold and time. Nothing can be more fun when enemy can't attack but you can.
2) If you have foot soldiers (swordsmen or spearmen), then go for spearmen to start with as they are a lot cheaper and can advance you faster. Their upgrades are cheaper as well.
3) Buy the first window upgrade to get two more archer slots and place two archers in them.
4) Dont wait for wave to end to buy upgrades. To go to upgrade screen simply press Space and this will pause the game and take you to upgrade screen.
5) After that focus on spearmen and archer and take them to one less than max upgrade level.
6) Then buy the 3rd gold for kill upgrade. This will help to boost your gold generation further.
7) Now since your gold starts to accummulate, buy population and gate health upgrades as well.
8) One important tip, dont make any more melee units if you are going to lose a wave unless you are sure they will survive to see the next battle. Placing a couple of units in front of dozen enemies is a total suicide.
9) If you have lost 2 gates then enemies AI will automatically send every new unit generated to the third gate. You mass up units very close to third gate.
10) After you have accummulated a lot of gold and bought all upgrades, it just boils down to fast clicking to place units. That is fun as well!
If you lose any mode first time, you will get to keep unlocked windows, next time you try it. That ways you wont have to spend any gold on unlocking windows. Also all unlocked powers will be available since wave 1. I hope you like the game as much as I enjoyed making it. You may leave your comments and ideas in the comment section on the game.