The Last Kids on Earth (season 1)

It turned out that the planet is captured by zombie apocalypse that didn't give a chance of survival for many people. The main characters are in their tree house and enjoy life. From time to time they manage to play games, eat candies and just admire the view from the tree. But the beauty of wildlife has long stopped impressing them. Becuase the protagonists are at the center of raging apocalypse.