Goodies can be picked up to become faster and stronger. Additional lives can be earned by combining specific bubbles or by achieving certain numbers of points.
When moving from level to level, it becomes tougher and tougher to beat the bad guys, that come in different shapes and fashions, each of them exhibiting different dangerous assets, in their quest to prevent you to be reunited with your lovely girlfriend dragon.
Be fast, and put those evil monsters in a bubble, destroy them and move on to the next level. But don't be too slow, because when you run out of time, you'll be chased by a major monster that can't be destroyed.