Similar to probably a hundred other games in the Android Market, Marble Blast requires you to shoot monochromatic bubbles at other monochromatic bubbles. Create a cluster of three or more, and all of them pop and disappear. The object, of course, is to clear your screen of all of them.
What makes Marble Blast unique, however, is that the bubbles, or marbles, actually travel around your screen in a single-file line. They aren't stationary targets anchored to the top of your screen as they are in other bubble-based games like Bubble Blast 2. Your job in Marble Blast is to clear all the marbles before they make their way into the hole at the end of their path, which can be difficult because the line is constantly moving and curving in different directions around your screen. Luckily, there are bonus bubbles that occasionally pop up throughout the levels, which can help by slowing the line of marbles down or stopping it from moving altogether.
Also, to keep the game interesting, your bubble-firing weapon changes location and the marbles travel a different path on each level.
Of all the bubble-based puzzle games out there, Marble Blast is definitely one of my favorites. Shooting is responsive and accurate, and the variations in levels make it incredibly addicting. Overall, I highly recommend the download.