In any game about attack and defensive towers player evaluates the quality of levels.
If you make them too straight, the project will be too casual and players quickly will be bored.
If you do amazing maze with lots of surprises, building a defense can be not a trivial task and trigger some negative emotions.
How to find a happy medium?
Through trial and errors, analyzing the behavior of the audience, long hours of work a game designer in tandem with graphic designer, producer of the project, a team of testers and other important people ...
Level design in our games has been appreciated by millions of players, join;) http://buff.ly/1DPmLHt