body { 
  margin: 0px;
}
.container {
  height: 100vh;
}

.header {
  background-color: gray;
  height: 10%;
} 

.content {
  height: 70%;
  display: flex;
  justify-content: space-between;
}

.footer {
  background-color: purple;
  height: 20%;
}

.box {
  background-color: blue;
  height: 15%;
  width: 100%;
  
}

.main-body {
  background-color: red;
  height: 100%;
  width: 50%;
}

.box-container {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  width: 50%;
}

.nav {
  list-style: none;
  display: flex;
  justify-content: space-around;
  padding: 0;
  margin: 0;
  height: 100%;
  align-items: center
}

.nav li {
  font-size: 20px;
}

@media (min-width: 1024px) {
 .conent {
   display: block;
  }
}

@media (max-width: 640px) {
 .content {
   flex-direction: column;
   justify-content: center;
   align-items: center;
 }

  .box-container {
    width: 80%;
 }
  
 .box {
   width: 100%;
 }
  
 .main-body {
   width: 80%;
  }