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

    @media screen and (min-width:501px){
       h1{ 
        font-size: 2.5rem;
       }
    }
    @media screen and (max-width:500px) {
        h1{
        font-size:1.5rem;
        }
    }

    @media screen and (min-width:640px){
        html{
        background-color: #eaf6ff;
        }
    }

    #fixed-size-grid-items ul{
    padding-left: 0;
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    }


    aside{
        width: 170px;
        margin: 10px;
        font-size: .8rem;
    }

    #stretchable-grid-items ul{
        list-style: none;
        display: flex;
        flex-wrap: wrap;
        margin-left: -10px;
        margin-right: -10px;
        margin-top: 1rem;
        margin-bottom: 1rem;
      }
  
      #stretchable-grid-items li{
        width: 100%;
        
      }
  
      @media screen and (min-width:480px){
        #stretchable-grid-items li{
          width: 50%;
        }
      }

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