这是一款Android壁纸应用，自从500px api关闭后，500Firepaper的壁纸源也切换到reddit的earthporn了，不过由于我依然想用500px，所以自己做了一个替代品
This is an Android Wallpaper App, since 500px close their api, 500Firepaper change it's picture source to Reddit's earthporn. As I still want to use 500px as the source, so I develop this alternate app.