body { 
 margin: auto;
 height: auto;
 background-color: black;
}

video { 
 width: 100%; 
 display:block;
 margin: auto;
 margin-top: 1%;
}
@media only screen and (min-width: 768px) {
  video {   
    width: 50%; 
  }
}

#but_start { 
  font-family: 'Oswald', sans-serif;  
  font-size: 150%;
  border: 0px solid white; /*rgba(0,0,0,1);*/
  height: 1%;
  width: 100%; 
  background-color: white; /*rgba(110,110,110,1);*/
  outline: none;
  display: block;
  margin: auto;
  margin-top: 0%;  
  cursor: pointer;
}
@media only screen and (min-width: 768px) {
  #but_start {   
    width: 50%; 
  }
}

#but_start:hover { 
  background-color: rgba(127,127,127,1.0); 
  border: 0px solid rgba(127,127,127,1.0);
}
#but_start:focus { 
  background-color: rgba(127,127,127,1.0); 
  border: 0px solid rgba(127,127,127,1.0);
}