style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300&display=swap');

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

body{
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background-image: linear-gradient(to right, #295270, #524175);
}

.main{
    width: 370px;
    padding: 30px;
    border-radius: 4px;
    background-color: #FFF;
}

.main header{
    font-size: 25px;
    font-weight: 500;
    text-align: center;
}

.main #form{
    margin: 40px 0 20px 0;
}

.form :where(input, select, button){
    width: 100%;
    outline: none;
    border: 1px solid #999;
    border-radius: 3px;
}

.form p{
    font-size: 18px;
    margin-bottom: 5px;
}

.form input{
    height: 50px;
    font-size: 17px;
    padding: 0 15px;
}

.form input:focus{
    border: 2px solid #524175;
}

.form .opcoes{
    display: flex;
    margin-top: 20px;
    align-items: center;
    justify-content: space-between;
}

.opcoes select{
    font-size: 16px;
    padding: 5px 20px;
}

.form .valor-conversao{
    font-size: 17px;
    margin: 20px 0 30px;
}

.form button{
    height: 52px;
    color: #FFF;
    font-size: 17px;
    cursor: pointer;
    background-color: #524175;
    border: none;
}