Crimsonland is a prime example that great graphics and sound aren't needed to make a great game
Aliens - just simple large claws with a large head
Zombies - naked humans
Lizards - typical lizard
Spiders - spiders with natural designs
These creatures come in different colors and sizes, so there's some variety in the color palette. Now the part of the gameplay comes to killing these creatures, cause they'll work just as hard to kill you. You'll be given a variety of weapons at your arsenal, and they're all pretty good and unique, each having its own advantages and disadvantages. With these, you get perks, which, like perks, give benfits (or sometimes de-benefits) in your quest against these monsters, there are around 40 of these and 25 weapons (with a few secret ones also), and then you have the typical bonus items as in most arcade games. You'll also meet a few bosses at every 10th level of the 50 level quest (100 adding Hardcore mode).
Where the game's gameplay does become more enjoyable is when you hear the music, since the grunts and screams aren't all that amusing. The music is great, and the extra downloadable music is great too. There are more modes other than the Campaign or Quest mode, the Rush - where a huge horde of aliens come running towards and you're only left with an unlimited assault rifle, the Survival - your typical shooter survival mode, and Typ'O Shooter - which can be used as a typing practice and requires you to type the word above an enemy to kill it.
Overall, Crimsonland is an enjoyable shooter that can last you forever with its outstanding gameplay.