*{
 
  margin: 0;
  padding: 0; 
  box-sizing: border-box;
}
body{
  background-color: #2c3e50;
  width: 100vw;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
.container{
  max-width: 800px;
  background-color: #ecf0f1;
  border-radius: 3px;
  box-shadow: rgba(17, 17, 26, 0.1) 0px 1px 0px;
}

#nav-tab{
  list-style: none;
}
#nav-tab li{
  display: inline-flex;
}
#nav-tab li a{
 text-decoration: none;
 color:rgba(0,0,0,0.5);
 padding: 10px;
 font-weight: 600;
 transition: background 0.5s;
}

#nav-tab li a:hover,
#nav-tab .active a{
  color:#fff;
  background-color: #e74c3c;
}

.page{
  display: none;
  min-width: 800px;
  min-height: 500px;
  border:5px solid rgb(248, 244, 244);
  border-top-color:#e74c3c;
  padding: 10px;
}

.page.page-active{
  display: block;
}

.page h2{
  font-weight: 600;
  margin-bottom: 10px;
  color:#2c3e50;
}