style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, Helvetica, sans-serif;
}

body {
    background-color: lightblue;
    min-width: 360px;
}

body>noscript {
    width: 100%;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.4);
    position: absolute;
    z-index: 100;

}

body>noscript>div {
    background-color: #fdefef;
    color: #dc2535;
    padding: 20px;
    box-shadow: 4px 4px 7px 1px #666666;
    max-width: 50%;
    min-width: 300px;
    text-align: center;
    position: relative;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}

body>h1 {
    text-align: center;
    margin-bottom: 20px;
}

body>div {
    padding: 0 20px;
}

body>div h3 {
    margin: 8px 0;
    position: relative;
    display: inline-block;
    left: 50%;
    transform: translateX(-50%);
    border-bottom-style: solid;
    border-bottom-width: 2px;
    cursor: default;
}

body>div textarea {
    display: block;
    padding: 10px;
    line-height: 20px;
    width: 100%;
    height: 200px;
    outline: none;
    resize: none;
    border-style: none;
    border-radius: 10px;
    font-family: 'Courier New', Courier, monospace;
    font-weight: bold;
}

#output {
    cursor: default;
}

.btn {
    display: block;
    margin: 10px auto;
    border: none;
    outline: none;
    padding: 10px 15px;
    background-color: black;
    color: white;
    border-radius: 20px;
    cursor: pointer;
}
#input-block{
    position: relative;
}
#btn-clear{
    position: absolute;
    margin: 0;
    padding: 5px 10px;
    top:10px;
    right: 10px;
    opacity: .3;
    transition: opacity 300ms;
}
#btn-clear:hover{
    opacity: 1;
}