.container {
  display: grid;
  grid-template-areas:
    "header header"
    "menu content"
    "footer footer";
  grid-template-columns: 1fr 5fr;
  gap: 3px;
  background-color: dodgerblue;
  padding: 5px;
}
.container div {
  background-color: white;
  padding: 10px;
}
.container div.header {
  grid-area: header;
  text-align: center;
}
.container div.menu {
  grid-area: menu;
}
.container div.content {
  grid-area: content;
}
.container div.footer {
  grid-area: footer;
  text-align: center;  
}


@media (max-width: 1250px) {
  .container {
    grid-template-columns: 1fr;
    grid-template-rows: var(--header-height) 3fr auto;
    grid-template-areas:
      "header"
      "content"
      "footer";
  }
.container div.menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: 180px;
    height: calc(100vh - 50px);
    opacity: 1;
    grid-area: unset;
    transition: transform 0.3s ease;
    transform: translateX(-100%);  
  }
  
}