body{background:#000;}
.container{
  
     min-width:280px;width:100%;height:100%;position:fixed;background-image: url('../imgBts/main-background-40.jpg'); 

}


.photo{position:fixed;animation:round 16s infinite;opacity:0;}
@keyframes round{   
  25%{opacity:1;}
  40%{opacity:0;}
} 
img:nth-child(4){animation-delay:0s;}
img:nth-child(3){animation-delay:4s;}
img:nth-child(2){animation-delay:8s;}
img:nth-child(1){animation-delay:12s;}