The player window version is your chosen quick launch option. If keyboard input stops working, press fullscreen/unfullscreen to fix it.
REL1, or Rudimentary Eaglercraft Launcher 1, is a smooth, ad-free, no-nonsense Eaglercraft launcher that contains 1.5, 1.8, and 1.12, with an accompanying Eaglercraft server that is accessable from the game called "Eaglerland." Features that are planned include an update (u) selector with data from eaglercraft archives, more versions like betas, better css (please), and more.