body {
  background-color: #eee;
  height: 100vh;
  margin: 0;
  position: relative;
  overflow: hidden;
}

* {
  box-sizing: border-box;
}

#demo {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  display: flex;
  flex-direction: column;
  user-select: none;
}

#end-zone {
  min-height: 200px;
  background: white;
  padding: 10px;
  margin: 10px;
  box-shadow: 0 1px 4px 0 rgba(0, 0, 0, 0.3);
}
#end-zone header {
  padding-left: 10px;
  font-size: 12px;
}

.middle {
  flex: 1;
}

#letter-box {
  margin: 10px;
  padding: 10px;
  background-color: white;
  box-shadow: 0 1px 4px 0 rgba(0, 0, 0, 0.3);
  min-height: 119px;
}

#container {
  border: 1px solid #ccc;
  position: relative;
}

#scroll-box {
  white-space: nowrap;
  overflow-x: scroll;
}

.letter {
  width: 80px;
  height: 80px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.letter > div,
.cloned-letter {
  background-color: mediumvioletred;
  color: #fafafa;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  position: relative;
  width: 60px;
  height: 60px;
  cursor: move;
  box-shadow: 0 1px 4px 0 rgba(0, 0, 0, 0.5);
}
.letter > div.placed,
.cloned-letter.placed {
  background: cornflowerblue;
}

.cloned-letter {
  position: absolute;
}