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

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

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

@media (min-width: 640px) {
    h1 {
        font-size: 2.5rem;
    }
}

@media (min-width: 640px) {
  .container {
    display: flex;
    justify-content: space-between;
  }
}

ul {
    list-style: none;
    padding-left: 0;
    font-size: 0.8rem;
}

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

#fixed-size-grid-items aside {
    width: 170px;
}

#stretchable-grid-items ul {
    /* margin-left: 1rem -10px 1rem -10px; */
    display: grid;
    grid-template-columns: repeat(1, 1fr);
}

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

aside {
    margin: 10px;
}

@media (min-width: 480px) {
    #stretchable-grid-items ul {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 640px) {

    #stretchable-grid-items ul {
        grid-template-columns: repeat(4, 1fr);
    }
}