body,html{
  height: 100%;
}

iframe{
  border: 0; 
  width: 100%; 
  height: 100%;
}

.container {
  display: flex;
  height: 100%;
  position: relative;
}

.item {
  border: 1px solid #ddd;
  border-radius: 5px;
  height: 100%;
  width: 100%;
  margin-bottom: 2%;
  padding: 10px;
  position: relative;
}
.item + .item { 
  margin-left: 2%; 
}

.item:first-child{
  width: 300%;
}

.source_code{
  padding: 10px;
  background: #fff;
  display: none;
  width: 100%; 
  height: 100%;
  position: absolute;
  box-sizing: border-box;
  overflow: auto;
  top: 0;
  left: 0;
}

video{
  max-width: 100%;
}