Drag with the mouse to create select boxes of ships, then click to send them where you want them. "S" adds more ships, "R" resets the game, sort of.
You can play the Processing.js/HTML5 rendition or original Java version.
Best sentence that would have made no sense 10 years ago: "Galaxy Nexus: Android Ice Cream Sandwich Guinea Pig" (via reddit)
I've said this before but I'll say it again: Why do bad things happen to good people? To even out the good things that happen to bad people.