text: const bg_choice = ['bg_2','bg_3','bg_4'];
  
  $(() => {
  
  	function changeBg() {
  		let current = $('.bg').css('background-image');
  
  		let idx = bg_choice.indexOf(current);
  
  		let new_choices = (idx > -1) ? bg_choice.splice(idx, 1) : bg_choice;
  
  		let bg = new_choices[Math.floor(Math.random() * bg_choice.length)];
  
  		let img = 'url(./img/backgrounds/' + bg + '.webp)';
  
  		$('.bg').css('background-image', img);
  	}
  
  	changeBg(); 
  });