A Tower Defense game pretty much built from the ground up for casual audiences on mobile devices, Guard Of The Kingdom appears quite deep at first, a trick it achieves by telling you *nothing* about the units other than their prices, but once you've tested every unit out, the game ends up being literally one-dimensional.
Every enemy will walk past every tower you build. Some enemies are slow and others are fast, but none are immune to any particular type of tower. This means that Acid Acid Acid Ice is pretty much the only combination worth building, although I've achieved interesting results in Survival by building Acid Stone Acid Stone all along the bottom row to cluster enemies together.
Honestly, I can't hold this against the game TOO much, since this was kind of an "Aha!" moment for me. Sometimes Tower Defense games can get *too* well-balanced, to the point where the only reason to build one combination of towers over another boils down to semi-random idiosyncrasies of the pathing, movement speeds, and AI. If we assume the creators of the game are non-native english speakers, I'd rather play a simple game with an obvious right answer than a complex game with poor explanations of how units work.
What's really strange is, about halfway through the game, they start pitching puzzle levels at you where you only get to choose between three specific units. Unfortunately, there's only two of these, and one of them has acid included as one of the options, so you really don't get very far from your comfort zone. The entire game could have been like this. Instead, they give you all the units, do a couple of these restricted levels, then give you all the units back again. Maybe in playtesting, people weren't figuring out that you need to go acid in order to beat the later stages? I dunno. I felt like more could have been done with this mechanic, since it was the only time I was forced to actually think after solving a game which, with only one lane one damage type, and one best unit, seems predisposed to be very much solvable.
Overall, it's a tactically dull TD with slick polish and some incredibly solid coding. At first I couldn't believe it was powered by Flash, until I remembered that they probably developed it using CS5, targeting Mobile. The graphics have that look to them when you zoom in, like they were rasterized long ago, before the game was even compiled. These sprites have NEVER seen a MovieClip. And while that's generally a good thing in Flash, it betrays this game's DNA. It was built for casual gamers, and it shows. If you take that into account, it's not too bad.