Miniclip's Canyon Defense is another tower defense game—I know, I know—but this one has good pixel art and does things a little bit differently. First of all, there are no upgrades. That's the genre's equivalent of Marcel Duchamp putting a urinal in an art museum. Or is it? What if I told you this heresy against form also has time-based special abilities? And support buildings?
The interface is the usual: Click on a building to select it, click on a non-path part of the map to build it. Building costs money, and you can sell them, too. This time there are tabs for basic towers, advanced towers, and buildings. Unlocking the towers and buildings involves completing "quests" like building a required number of towers, or saving up a required amount of money; there are also requirements that the towers above the one you want in the menu are also unlocked. Placement is critical, as your towers must turn to target the enemies. Buildings provide the ability to launch a nuclear strike, place walls, or freeze time, all with a long cool-down period between each use, and some buildings also give passive benefits, or "buffs" (to you WoW veterans).
Analysis: The game works despite its departure from the conventional mechanics of the tower defense genre; however, the game is also similar to its cousins in one major respect: it suffers for severe tuning issues. The speed of the projectiles is just as fast as the fastest enemy unit, meaning that your missiles can chase the bugger in a straight line, right off the screen. Coupled with the painfully slow turning speed of the turrets, a property common to every tower, and you've got a game whose basic mechanic hinges on something badly in need of oiling. Then you've got the upgrade tree's highly inelegant structure, hanging like a sickly willow on way too many dependencies to intuitively make a strategy out of. It's not too late MiniClip, tune that spreadsheet! The support building sub-system does add an interesting tactical level to the genre.
If you want some fresh TD with a Mad Max aesthetic, play Canyon Defense.