There is a certain paradigm shift that must occur when playing this game for the first time before the light goes on and the player ‘gets it’. I believe this is due to a sort of cognitive bias we have as gamers: when firing a turret we expect things to explode… and to go fast.
However, this game is anything but fast. The gameplay forces the player to slow down, think first, and to plan each shot carefully. Each game therefore becomes a careful placement of orbs rather than a quick-fire session to arrive at the end result. The slower pace gives way to excitement as an orb inches ever so close to that fearsome dotted line, and strategy emerges as the key ingredient to an award winning recipe. Those who don’t experience the paradigm shift may never appreciate the subtlety and the genius of this very simple gameplay design.
There’s also a version for the iPhone called Orbital.
Update: Here’s a Java version with rotation.