body{
    max-width: 800px;
    margin-left: auto; margin-right: auto;
    width: 90%;
}
@media (min-width: 640px){
    body{
        background-color: #eaf6ff;
    }
}
@media (max-width: 500px){
    h1{
        font-size: 1.5rem;
    }
}
@media (min-width: 640px){
    h1{
        font-size: 2.5rem;
    }
}
.first {
  display: flex;
  flex-wrap: wrap;
  list-style: none;
  padding-left: 0;
  margin: 0;
}

.first li {
  margin: 10px;
}

.first aside {
  width: 170px;
  font-size: 0.8rem;
}
.second {
  display: flex;
  flex-wrap: wrap;
  list-style: none;
  padding-left: 0;
  margin: -10px;
}
.second li {
  width: 100%;
  margin: 10px;
}

@media (min-width: 480px) {
  .second li {
    width: calc(50% - 20px);
    }
}

@media (min-width: 640px) {
  .second li {
    width: calc(25% - 20px);
    }
}