It's a tower defense game. Search it on Newgrounds or Kongregate and you'll get an accurate idea of what this is. Enemies run along a set path that you set various types of towers around to kill them. allowing them to pass through the maze alive reflects negatively (the town takes damage until the health bar reaches zero), while killing all of them awards you with a Perfect Wave and a point bonus after the level. An interesting improvement on the formula is that you, as one of 16 characters from the series, can move about the map to build towers, collect money, and stop those few that got through the maze from reaching the end. Not only does it give all these advantages, but it beats trying to use the left stick like a mouse the way lots of console RTS games do. Each character also has a special ability, from Butters going into a tap dancing fit & killing any and all near him, to Kenny's "Welfare Check" that makes enemies drop random amounts of cash. It makes for some good strategy as to just what bonuses will or will not help you.
Starting it up, I wind up waiting for about 15 seconds while various credits and autosave notes appear that I really only need to see for not even 5, if at all. After getting through this, I found playing solo put me at an automatic disadvantage. You can only control 1 character at a time, and each one has certain jobs he/she is best for. Of the usual 4, Cartman is best for attacking, Kenny is good for long range, fast attacks, Stan is fastest, and Kyle has the most useful special attack of them all, causing all attacks to be 10 times as powerful for a time. Each has his disadvantages of course, as I quickly found out trying to stop Mongolians with Kyle was like Urkel beating Mike Tyson in a fight. Swapping characters is mapped to right bumper, and you have to cycle through until you find the one you wanted, which can often be messy. I know it's a small complaint, but they could have mapped this to the unused D-pad. The game rewards you for things you do by giving you episode clips and bios in a scrapbook, which feels really weak. Most of the episode clips are less than 10 seconds long, and don't give you enough to go off about the given character, rendering them pure fan service.
It will be very challenging if this is your first experience with tower defense. Once you realize that strength isn't in how many towers are out, but how well placed & upgraded your towers are, you'll be fine. An additional difficulty is unlocked after the campaign is finished, only for those who really know what they're doing.
I turned the music off after about 2 hours. It's not unbearable, but it's nothing I'd be proud of having made. The characters all appear to be voiced by the correct actors (likely considering Comedy Central was involved in development), but the lines feel either like patchy situational phrases put together, or quotes from the series. Comic-style cutscenes at the beginning and end of each level is where the writing shines with South Park's usual wit & humor, though the game reminds me of the Simpson's game in that certain situations in the game happen solely because the game needed more length. For instance, certain levels in campaign will have the boys poking fun at the chinese annoucner's accent, leading to situations like this.
ANNOUNCER: LEVER 8 COMPREETO! TWEEK UNROCKED!!
CARTMAN: WHY THE HELL WOULD FINISHING THIS LEVEL UNROCK TWEEK?!?
Maybe it's my comedic soft spot for breaking the fourth wall, but I can't help laughing at this.
This is what the game is made for, plain and simple. Playing solo puts you at a disadvantage as I've already stated, but get some friends together and let the tactics flow, and you can tackle any challenge the game throws at you.
The scrapbook can be described as weak. You work so hard to unlock that one clip of X character, playing the same level over and over again trying to get 500,000 points on a level you have trouble getting 200,000 on, just for a 10 second clip. Challenge mode levels become unlocked after every other level in campaign, and they are great time wasters. Tough, but great.
It's about as fun as you can expect a tower defense game to be, perhaps even a bit more so at times.