@charset "UTF-8"; 
body {
  background-color: gray;
}
 
#wrap {
  width: 960px;
  margin: auto;
  background-color: white;
}
 
header   {
  padding: 40px;
  height: 80px;
}
 
nav {
  padding: 8px 40px;
  background-color: black;
  color: white;
  transition-property: background-color;
  transition-duration: .5s;
}

nav:hover {
  background-color: dimgray;
}
 
main{
  padding: 40px;
  height : 400px;
}
 
footer   {
  padding: 40px;
  height: 40px;
  background-color : black;
  color: white;
}

.expansion {
  width: 500px;
  height: 300px;
  overflow: hidden;
}
.expansion img {
  width: 100%;
  transition: transform .5s;
}

.expansion img:hover {
  transform: scale(1.1);
}