header {
  background: purple;
  height: 70px;
  width: 100%;
  gap: 10px;
  display: flex;
  align-items: center;
  position: fixed;
  top: 0;
  padding-left: 100px;
}

#middle {
  margin-top: 70px;
}

main {
  background: yellow;
  height: 500px;
  flex-grow: 3;
  
}

aside {
  background-color: lime;
  height: 500px;
  flex-grow: 1;
}

footer {
  background-color: lightgray;
  width: 100%;
  height: 40px;
  margin-top: 10px;
}

button {
  background-color: cyan;
  width: 80px;
  height: 30px;
}

div {
  display: flex;
  height: 500px;
  margin: 0px 100px;
}