style.css

@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@100;300;400;500;700&display=swap');

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

body {
    width: 100vw;
    height: 90vh;
    background: #efefef;
    align-items: center;
    justify-content: center;
    display: flex;
}

main {
    width: 100%;
    padding: 30px;
    align-items: center;
}

h1{
    text-align: center;
}


/* FORMULARIO */
form {
    display: flex;
    flex-direction: column;
    margin: 10px;
    width: 40%;
}

/* DIV DOS INPUTS */
.form-group {
    margin: 10px;
    align-items: center;
}

.conteudo{
    display: flex;
    justify-content: space-around;
    align-items:center;
}

.input {
    width: 100%;
}

/* INPUTS */
input[type=number], input[type=text] {
    border: 1px solid #ececec;
    border-radius: 5px;
    padding: 5px;
}

/* BOTOES */
.botao {
    border: 1px solid #ccc;
    border-radius: 5px;
    padding: 5px;
    cursor: pointer;
}

#resultadoImc {
    border: 1px solid #ccc;
    width: 60px;
}

#aviso {
    font-weight: bold;
}


/* DIV #resultado */
#resultado {
    width: 40%;
    height: auto;
    border-radius: 5px;
    border: 1px solid rgba(90, 90, 90, 0.24);
    background: #fff;
    text-align: center;
}

/* paragrafos do resultado */
.pessoa {
    padding: 10px;
}
.pessoa:nth-child(odd) {
    background: #efefef;
}
.pessoa:nth-child(even) {
    background: #fff;
}