*{
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body{
     font-family: Arial, Helvetica, sans-serif;
    background-color: rgb(63, 193, 233);
}
.cajax{
    background-color: rgb(0, 195, 255) ;
    border: 2px solid black;
    height: 200px;
}
.cajay{
    background-color: rgb(9, 255, 0);
    border: 2px solid rgb(255, 40, 2);
    height: 200px;
}
@media screen and (max-width: 450px)and (min-width: 10px){
    .cajax{
        background-color: rgb(74, 6, 235) ;
        
        height: 200px;
    }
    .cajay{
        background-color: rgb(255, 0, 234);
       
        height: 200px;
    }
}    
@media screen and (max-width: 990px)and (min-width: 451px){
    .cajax{
        background-color: rgba(0, 255, 128, 0.945) ;
        
        height: 200px;
    }
    .cajay{
        background-color: rgb(0, 17, 255);
       
        height: 200px;
    }
}  
@media screen and (min-width: 991px){
    .cajax{
        background-color: rgb(255, 0, 0) ;
        
        height: 200px;
    }
    .cajay{
        background-color: rgb(218, 255, 11);
       
        height: 200px;
    }
    
    
}