clever and fun
a very good "engine", although it is slightly annoying when the wind changes direction and you don't notice it right away and miss your shot. nice graphics, too--the sprite are a bit cartoony, but they work well in context.
the addition of the movable shield was a very nice touch--takes some getting used to simultaneously firing and manipulating it, but adds a whole new level to the game.
the purchasable upgrades are also well-selected and well-balanced, and fun to decide between and use.
a small complaint would be the lack of visibility on some levels. this may be more of a personal preference, but IMHO if making it hard to see were the right way to make a game challenging, then DOOM 3 would have rocked.
this however, is a minor detail. on the whole, an awesome game and one of the best turret defenses on the site.