If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Toph and her friends need to reach Ba Sing Se on the other side of the dreaded Serpent's Pass. Use Toph's earthbending skills to repair the rocks so all her friends can safely cross. Blocks can be created when Toph's Chi is full. You can also collect tokens under the rocks for power-ups. Good luck!