*{padding:0;margin:0;overflow: hidden;}
img{width:100%}
#app{position:fixed;top:50%;left:50%;transform:translate(-50%,-50%)}
/* <768px */
@media screen and (max-width:768px){
.col{width:100%}
}
/* >=992 and  */
@media screen and (min-width:992px){
.col{width:49%}
}
/* >=768px and <1200px */
@media screen and (min-width:768px) and (max-width:1200px){
.col{width:48%}
}
/* >=1200px */
@media screen and (min-width:1200px){
.col{width:33%}
}