Ender's game

I already read more than half of the book called Ender's game. The most fascinating thing was that Ender beaten the game that couldn't be beaten. It is called the giant's drink and Ender killed the giant and not drinking either of the two drinks that were in the giant's table. I did not understand that he had beaten the game that couldn't be beaten, but he used another way of winning the giant and going to fairyland. Also, I am surprised that Ender became the most popular kid in the whole battle school. It is because Ender was the most least popular only months ago.