style.css

                                html {
                                    box-sizing: border-box;
                                }
                                
                                *,
                                *:before,
                                *:after {
                                    box-sizing: inherit;
                                }
                                
                                body {
                                    background: #f5f5f5;
                                    color: #333;
                                    font-family: arial, helvetica, sans-serif;
                                    font-size: 32px;
                                }
                                
                                h1 {
                                    font-size: 32px;
                                    text-align: center;
                                }
                                
                                p {
                                    font-size: 20px;
                                    line-height: 1.5;
                                    margin: 10px auto 0;
                                    max-width: 640px;
                                    display: inline-block;
                                }
                                
                                .main {
                                    background: #fff;
                                    border: 5px solid #ccc;
                                    border-radius: 10px;
                                    margin: 40px auto;
                                    padding: 40px;
                                    width: 80%;
                                    max-width: 700px;
                                }
                                
                                button {
                                    background: #fff;
                                    border: 2px solid #333;
                                    border-radius: 5px;
                                    color: #333;
                                    font-size: 16px;
                                    font-weight: bold;
                                    padding: 1rem;
                                }
                                
                                button:hover {
                                    background: #27AE60;
                                    border: 2px solid #27AE60;
                                    color: #fff;
                                }
                                
                                button.reset {
                                    background: #f03737;
                                    border: 2px solid #f03737;
                                    color: #fff;
                                    float: right;
                                }
                                
                                button.reset:hover {
                                    background: #fff;
                                    border: 2px solid #f03737;
                                    color: #f03737;
                                }
                                
                                input {
                                    border: 2px solid #333;
                                    border-radius: 5px;
                                    color: #333;
                                    font-size: 25px;
                                    margin: 0 0 20px;
                                    padding: .5rem 1rem;
                                    width: 100%;
                                }
                                
                                #demo1 {
                                    border: 2px solid #333;
                                    border-radius: 5px;
                                    background-color: #e9e9e9;
                                    word-wrap: break-word;
                                    font-size: 15px;
                                    color: rgb(0, 0, 0);
                                    margin: 0 0 20px;
                                    padding: .5rem 1rem;
                                    width: 100%;
                                    font-family: arial, helvetica, sans-serif;
                                }
                                
                                #demo2 {
                                    border: 2px solid #333;
                                    border-radius: 5px;
                                    background-color: #e9e9e9;
                                    word-wrap: break-word;
                                    font-size: 15px;
                                    color: rgb(0, 0, 0);
                                    margin: 0 0 20px;
                                    padding: .5rem 1rem;
                                    width: 100%;
                                    font-family: arial, helvetica, sans-serif;
                                }
                                
                                #Bcopy {
                                    float: right;
                                    padding: 2px;
                                    font-size: 15px;
                                }
                                
                                #Bcopy:hover {
                                    background: #3d3d3d;
                                    border: 2px solid #3d3d3d;
                                    color: #fff;
                                }