Neutrino 1.1

I updated the gameto version 1.1.

•  the gamenow starts in fullscreen, which scales the game a bit bigger, switching to borderless window mode with alt + enter is still possible
• added markers that appear around the player and the enemies in the first
  wave, to help getting into the game, the markers disappear after the first wave is defeated
• changed the logic for shield powerups a bit to make the game more difficult