Processed Tower Defense is a strategy game where you try to defeat waves of dangerous monsters before they reach your tower. Of course, its less of a tower and more of a blueish square on the right side of the screen, but the idea stands.
Monsters appear on the only colorful square on the far left edge of the map, sprint towards the only colorful square on the far right edge of the map. Each time a monster reaches your tower, you lose one life. Lose all of your lives and the game ends.
You start out with a small treasury of gold, and each time you defeat a creep you receive a bit more gold to aid in your valiant defense of the lame blue squa... I mean... your tower. You also receive a few more points to your score when you defeat a creep. While gold can be redeemed for more powerful towers, score can only be redeemed as social capital among fellow PTD players, and thus could be fairly described as both invaluable and worthless.
Towers are your first and last line of defense against creeps. Except for the bomb and the nuke, but thats not the point right now. We're talking about towers, okay? Keep on task, won't ya?
Towers all have another helpful characteristic: they block the paths of creeps. This lets you build complex mazes in the hope that the creeps will become dizzy and stop for a few moments to recover over a nice cup of tea. At the bare minimum you'll get to shoot at them for longer.
Creeps are the evil scourge which long to plaster the sickening Game Over message at the top of your screen. Resisting them is your calling, your purpose, your afternoon you were supposed to spend doing laundry.
Each of those categories of creeps can also have one additional behavior. Some creeps are very slow crossing water, some climb mountains at shocking speeds, and some even fly over your towers while mocking the effectiveness of your intricate designs.
Each square on the board is a certain type of terrain. Terrain is randomly assigned each time the game is played, and bestows certain effects upon towers and creeps inside of them.
The Bomb is the first of two last resort weapons at your disposal. You have an unlimited supply, but they get a bit more expensive with each passing level. Will severely damage all creeps in its radius (dealing 75% of their max hitpoints), but won't come cheap.
The Nuke is the last resort weapon of last resort weapons. It will destroy all creeps on the screen, but has two drawbacks. First, you won't recieve any loot from creeps destroyed this way. Second, you only have a limited supply and have no way to replenish that supply once they are exhausted.