Any easier/fair TD games out there???

[proof21]

I find a lot of TD games up their difficulty about mid way through the campaign in order to push you to buy IAP, worst offenders of this are Elf Defence and Lost Earth, in which the easy setting even becomes too difficult to complete without IAP.

The one TD game I found to be fair was Kingdom Rush....which is the best of the best anyways. Creeps was also fair, but some of the bosses seemed way too hard to defeat.

So is there any good TD game out there that isn't pushing for IAP and actually has a fair difficulty?

Thanx