@charset"UTF-8";

*{
    box-sizing: border-box;
}

html{
    height: vh100;
    font-size: 62,5%;
    font-family: sans-serif;
}


#contenedor {
    width: 100%;
    margin: auto;
}

<style>
@import url('https://fonts.googleapis.com/css?family=Roboto');
</style> 


body{
    background-color: whitesmoke;
    margin: 50;
    width: 100%;
  
}


nav {background-color: #6ac9f4; }

* {box-sizing: border-box;
    font-family: sans-serif;
    color: #001b36
}

ul{ 
    display: flex;
    list-style: none;
    padding: 2em;
    margin: 0;
}
    
header nav ul li a {
    text-decoration: none;
    text-align: center;
    font-family: roboto;
    background-color: #dcdcdc;
    display:block;
    padding: .5rem;
    color: #001b36;
    border-bottom: rgb(106, 201, 244) .2rem solid;
    margin-left: 50px;
    margin-right: 60px;
    font-weight: bold;
        
}  

header nav ul li a:hover {
    color: white;
    background-color: lightslategray
}

.destaque{
    background-color: #001b36;
    color: white;
    font-weight: bold
}

h1,h2,h3 {
    font-family: sans-serif;
    text-align-last: left;
    font-size: 17px;
    background-color: #b2d8ea; 
    font-family: roboto;
    color: #001b36
    
    
}


h4 {
    font-family: sans-serif;
    color: gray;
    text-align-last: left;
    font-size: 0.9rem;
    
}


section { 
    color:  rgb(160, 234, 225);
    font-family: serif;
    text-align-last: left;
    padding: 5px;
    

}

article img {
    padding: 10px;
    width: 30em;
    height: auto;
    margin-top: 1rem;
    margin-left: 0rem;
}


article {
    color: rgb(160, 234, 225);
    padding: 5px;
}
    


footer { text-align: center;
    font-family: sans-serif;
    color: white;
    padding: 1rem;
    font-size: 7pt;
    text-align: center;
    padding: 1rem;
    background-color: #6ac9f4;
   
}

@media screen and (max-width: 30em){
    
    body{background-color: #6ac9f4;}
    
    h1,h2,h3 {
    font-family: sans-serif;
    text-align-last: left;
    font-size: 17px;
    background-color: #f2fbff; 
    font-family: roboto;
    color: #001b36;
    
}
   img {
    margin-left: 0px;
    align-content: center;
    padding: 10px;
    width: 20em;
    height: 13rem;
    margin-top: 1rem;
    margin-left: 0rem;
   
     
}
     article  img {
    margin-left: 0px;
    align-content: center;
    padding: 10px;
    width: 20em;
    height: 13rem;
    margin-top: 1rem;
    margin-left: 0rem;
   
     
}
    
    

 
  

nav {background-color: #f2fbff; }
 
   
    
    header {
        list-style: none;
        text-align: center;
        display: block;
    }

 header ul {
    list-style: none;
    padding: 0.7em;
    margin: 0;
    display: block;
    }
    
    header  nav ul li a {
        text-align: center;
        padding: .3rem;
        margin: 0;
        display: block;
    }
 
    
}