*{margin: 0;padding: 0;box-sizing: border-box;}
*::after,
*::before{
  box-sizing: border-box;
}
body{
    height: 100vh;
    display: flex;
    flex-direction: column;
}
.code-wrapper{
   flex:0.3;
   height: 30%;
   padding: 10px;
}
.preview-wrapper{
    flex: 0.7;
    height: 70%;
}
#code{
    overflow: hidden;
    height: 100%;
}

.action{
    position: absolute;
    right: 0;
    top: 0;
    display: flex;
    flex-direction: column;
}
.action>button{
    margin: 10px;
    padding: 8px 10px;
    background: #ddd;
    border: none;
}
.action>button.active{
    box-shadow: 1px 1px 1px rgba(0,0,0,0.8)
}
.action>button:focus{
    outline: none;
}

ul {
    display: table;
    list-style: none;
    margin: 0 auto;
    max-width: 800px;
    padding: 0;
}
 ul li {
    display: inline-block;
    float: left;
 }