style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    outline: none;
}

html {
    font-family:'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(45deg, #F5F7FA, #B8C6DB);
    background-attachment: fixed;
}

.flex-container {
    display: flex;
    justify-content: space-evenly;
    width: 100%;
    margin-top: 10%;
}

.input {
    box-shadow: 0 0 1px #fff;
    background-color: #fff;
    height: 300px;
    width: 500px;
    padding: 1%;
    border-radius: 5px;
    text-align: center;
}

.input textarea {
    width: 450px;
    height: 200px;
    border: none;
    border-radius: 5px;
    padding: 2%;
    font-size: 15px;
    font-family: Arial, Helvetica, sans-serif;
    resize: vertical;
    background-color: #dfe4ea;
}

.input button {
    width: 100px;
    height: 40px;
    border: none;
    border-radius: 5px;
    margin-top: 3%;
    cursor: pointer;
    transition: .2s;
    background-color: #57606f;
    color: #fff;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-size: 16px;
}

.input button:hover {
    background-color: #2f3542;
}

.output {
    width: 500px;
    box-shadow: 0 0 1px #fff;
    background-color: #fff;
    border-radius: 5px;
    font-weight: lighter;
}

.output h2 {
    text-align: center;
    font-size: 26px;
    padding-top: 1%;
    color: #000;
    font-weight: lighter;
}

.output ul {
    margin: 10%;
    font-size: 20px;
    list-style-type: none;
}

.output span {
    font-weight: bold;
}