I play a lot of TD games. I love TD and strategy games.
This game is like babies first TD. It has 4 possible towers and all the positions for tower placements are made for you.
There is an archer tower which fires fast but does light damage, mage tower which pirces armor units, siege towers which do aoe splash, and barracks which produce units to block creeps.
There is no slow towers so you have to rely on barracks to block creeps so your other towers can do something. Barracks only spawn 3 units so if there are more than 3 creeps coming then they will walk on by. The siege towers are useless because of the lack of slow. There is no point in aoe in this game. The mage towers are also lacking since they are much slower than the archers and armored units are few and far between. The strategy is reduced to spaming archer towers and barracks. Pretty boring.
It does have hero units ala some Warcraft 3 td maps but you bearly control it. You tell it where to stand and it does everything else on its own.
You have 2 hero powers. One to spawn 2 units and the other to summon a small firestorm. Both of these powers quickly become useless unless you upgrade them. However, upgrading them means you arent upgrading your towers which makes it stupid.
The story is nothing to talk about. Its toled through about 2 sentences before every mission. Throw away.
All in all this TD is extremly basic and really shows its mobile origin. If you love TDs you might be ok picking it up on sale for a buck but otherwise leave it be.