Clean Asia! is a hardcore shmup that consists wholly of boss battles, carried in what appears to be vector graphics. There are three levels (called Thailand, New Korea, and China, hence the title), with different boss behaviors for each. What's unique and original about the game, however, is that your objective isn't so much shooting enemies as smashing enemies into debris, and then collecting that debris magnetically.
You have a choice of two ships: the Attractor, which attacks by triggering a fast thrust and ramming into your opponent, and the Reflector, who shoots like a more normal shmup ship. In either case, once you've smashed or shot a piece of an opposing boss, you need to press a key to attract the debris to you. You "level up" by attracting 100 pieces of debris.
Naturally, all the bosses shoot at you, in different ways, and you need to dodge their fire while positioning yourself to defeat them; shmups tend to divide into ones with gentle learning curves and ones with fierce action that appeal more to serious shmuppers who have the skillz to manage them. Clean Asia! is definitely in the second camp.
It's pretty short, but the gameplay is unique -- and it's an IGF nominee (in both the Visual Art and Audio categories -- nice techno score), and Cactus, its creator, is one of our most interesting indie auteurs.