style.css

body{
    display: flex;
    flex-direction: column;
    box-sizing: border-box;
    min-height: 100vh;
    margin: 0;
    padding: 0; 
    font-size: 1.2rem;
}
header{
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 2rem;  
    background-color:#00293F ;
    color: white;
}
header,footer{
   max-width: 100%;
}
nav ul{
    display: flex;
    margin: 0;
    padding: 0;
}
.logo a{
text-decoration: none;
color: white;
}
nav li{
    list-style: none;
    font-size: 1.2rem;
}
nav li > *{
    margin-left: .8em;
}
nav a{
    color: white;
    text-decoration: none;
}
nav a:focus,
nav a:hover,.logo a:hover{
    color: yellowgreen;
}

footer{
    display: flex;
    justify-content: space-evenly;
    align-items: center;
    margin-top: auto;
    background-color: #00293F;
    color: white;
    
}

@media(max-width:420px){
header{
    flex-direction: column;
    justify-content: space-evenly;
    
}
.logo,nav ul{
    align-items: center;
    padding: 10px;
}
footer{
    flex-direction: column;
    align-items: center;
}
}

@media(max-width:270px){
    header{
        align-items: center;
        padding: 0;
    }
  .logo{
      margin-bottom: 0;
  }
    nav ul{
    flex-direction: column;
    align-items: center;
    }
   
}