Fuzetsu and Lash
The miniscule Fuzetsu was Jos Hirth's entry in the Java 4k competition—he placed fifth! The restrictions placed on Fuzetsu's size are reflected in the extremely basic graphics and gameplay. Each level consists of a boss, a red sphere, that releases beautiful streams of bullets. Use the mouse to control your ship, a white pixel surrounded by a blue field, and get as close to the enemy bullets as you can without touching them. The more bullets inside the field surrounding your ship, the more shots of your own will be released. Fuzetsu is a Java Web Start application, which requires the Java Runtime Environment. Click.
If you prefer to avoid danger rather than being forced to seek it out, HIZ's Lash is a shmup with a defensive twist. Use the blue line attached to your ship to sweep the screen clean of certain enemies and bullets. The line moves clockwise as your travel right or up, and counterclockwise as you move left or down; lock it to its current angle by pressing [X] or [shift], and fire bullets of your own by pressing [Z] or [ctrl]. Pressing [enter] restarts, and you can pause by pressing [space], although this seems buggy. Lash is fast and generous, with 10 lives on every difficulty level, but I almost wish it was as simple as Fuzetsu. Why not remove the ability to shoot and make Lash entirely about mastering the blue line? Click.