style.css

body {
    background-color: #292929;
    font-family: sans-serif;
}

.container {
    width: 500px;
    margin: 0 auto;
    background-color: #292929;
    padding: 20px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
    border: 1px solid #3f3f3f;
}

.input {
    margin-bottom: 20px;
}

.input input {
    width: 100%;
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    outline: none;
    box-sizing: border-box;
}

.input button {
    padding: 10px;
    border: none;
    border-radius: 5px;
    color: #fff;
    cursor: pointer;
    outline: none;
}

.output textarea {
    width: 100%;
    padding: 10px;
    border: 1px solid #555555;
    border-radius: 5px;
    outline: none;
    box-sizing: border-box;
    resize: none;
    height: 200px;
}

#result {
    background-color: #292929;
    color: #ffffff;
}

#result:focus {
    outline: none;
}

#result::-webkit-input-placeholder {
    color: #ccc;
}

#result::-moz-placeholder {
    color: #ccc;
}

#result:-ms-input-placeholder {
    color: #ccc;
}

#result:-moz-placeholder {
    color: #ccc;
}

#prompt::-webkit-input-placeholder {
    color: #ccc;
}

#prompt::-moz-placeholder {
    color: #ccc;
}

#prompt:-ms-input-placeholder {
    color: #ccc;
}

#prompt:-moz-placeholder {
    color: #ccc;
}

#prompt:focus {
    outline: none;
}

#generate:hover {
    background-color: #0097a7;
}

#generate:active {
    background-color: #00838f;
}

#prompt {
    background-color: #3b3b3b;
}

#prompt, #code {
    color: #ffffff;
}