@media screen and (max-width: 600px){
.sa{
/*background:yellow;*/
width:1000px;
height:900px;
display:flex;
flex-direction:column;
justify-content:center;
text-align:center;
align-content:center;
}
.se{
/*background:blue;*/
width:400px;
height:500px;
margin-top:100px;
}
.si{
/*background:purple;*/
width:400px;
height:400px;
margin-left:50px;
margin-top:100px;
}

img{
width:300px;
height:300px;
margin-top:100px;
}
.ra{
color:white;
border:0px;
border-radius:7px;
background:blue;

}
.re{
color:blue;
}
.ri{
color:orange;
}
}

@media screen and (min-width: 600px){
.sa{
/*background:yellow;*/
width:1000px;
height:900px;
display:flex;
flex-direction:row;
justify-content:center;
text-align:center;
align-content:center;
}
.se{
/*background:blue;*/
width:400px;
height:500px;
margin-top:100px;
}
.si{
/*background:purple;*/
width:400px;
height:400px;
margin-left:50px;
margin-top:100px;
}

img{
width:300px;
height:300px;
margin-top:100px;
}
.ra{
color:white;
border:0px;
border-radius:7px;
background:blue;

}
.re{
color:blue;
}
.ri{
color:orange;
}
}