A downloadable game for Windows, Mac OS X, and Linux
Ground Control is an arcade-styled shoot-em-up made with the Mercury game library. The gameplay itself is simply about shooting down attack balloons during World War IV, in which technology has digressed after the nuclear catastrophe that ended World War III.
It's pretty simple, but fun as hell.
Arrow keys to turn left/right
Space to fire
Java 1.7 or higher
REQUIRES JAVA 1.7+ TO RUN!
Download the JAR, and assuming Java is installed correctly, open it.
If you have any major problems try running it from the command line.