If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Rotate a gem one space at a time clockwise or counter clockwise to line up 3 or more gems of the same color. You can also line up 3 or more gems by moving a column toward or away the center jewel. Matching rows of gems earns you points that power up the center jewel. When it is completely powered up, you advance to the next level!