body{
    max-width: 800px;
    max-width: 90%;
    margin-left: auto;
    margin-right: auto;
}

@media (min-width: 640px)
{
    html{
        background-color:#eaf6ff ;
    }
    h1{
        font-size: 2.5rem;
    }
}

@media (max-width: 500px)
{
    h1{
        font-size: 1.5rem;
    }
}

li{
    list-style-type: none;
  }
  
ul{
    padding-left: 0px;
  }
  
#fixed-size-grid-items ul{
    display: flex;
    flex-wrap: wrap;
    font-size: 0.8rem;
  }
  
#fixed-size-grid-items aside{
    width: 170px;
    margin: 10px;
  }

#stretchable-grid-items ul{
    display: flex;
    flex-wrap: wrap;
  }

#stretchable-grid-items li{
    width: 100%;
 }  

@media(min-width: 480px){
    #stretchable-grid-items li{
       width: 50%;
    }  
}

@media(min-width: 640px){
    #stretchable-grid-items li{
       width: 25%;
    }  
}


#stretchable-grid-items aside{
    margin: 10px;
  }

#stretchable-grid-items ul{
    margin-left: -10px;
    margin-right: -10px;
    margin-top: 1rem;
    margin-bottom: 1rem;
    }