caper::game_loop!

macro_rules! game_loop {
    ( $input:ident, $renderer:ident, $shaders:ident,
      $cam_state:ident, $render_items:ident, $text_items:ident,
      start => $start:block,
      update => $update:block,
      $ui:ident => $ui_update:block) => { ... };
}

quick macro to use in the examples for easily defining all the modules and game loop