Designed to be unbalanced for that "level up" feeling and to encourage spending money. Bleh. Automatic points off as well for in-game solicitation of 5 star ratings. Use your screen space to make the game better, not to beg for rating handouts.
Graphics and such are nicely polished, but it needs more attention to basic usability. To the commonly mentioned lack of hotkeys and showing tower data, I would add this: HUD elements like the level up bar should NEVER obscure vital information. For instance, on level 12, is that a start or a finish? Guess wrong, and now I get to start over. Maybe not a big deal, but minor annoyances like this add up to a negative game experience.
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