style.css

body {
  padding: 0;
  margin: 0;
  background-color: #39677e;
  background-repeat: no-repeat;
  background-size: cover;
}

#flex-container {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
  font-family: Cambria, Cochin, Georgia, Times, "Times New Roman", serif;
}

.conteudo {
  background-color: whitesmoke;
  padding: 40px;
  border-radius: 20px;
  width: 280px;
  -webkit-border-radius: 20px;
  -moz-border-radius: 20px;
  -ms-border-radius: 20px;
  -o-border-radius: 20px;
}

.cabecalho {
  padding-bottom: 50px;
  opacity: 0.8;
  text-shadow: 0px 4px 4px rgba(0, 0, 0, 0.25);
}

.cabecalho::after {
  content: "";
  width: 30px;
  height: 3px;
  background-color: #0f597d;
  display: block;
  margin-top: -18px;
  margin-left: -1px;
}

.card_conteudo label {
  font-size: 20px;
  opacity: 0.8;
}

.conteudo_area {
  display: flex;
  flex-direction: column;
  padding: 10px 0 2px 0;
}

.conteudo_area input {
  margin-top: 10px;
  padding: 2px 5px;
  background-color: transparent;
  border: none;
  border-bottom: 3px solid #bdb8b8;
  outline: none;
  font-size: large;
}

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

.recuperar_senha {
  text-align: center;
  width: 60%;
  text-decoration: none;
  color: #c91818;
  margin-top: 20px;
}

.conteudo_verificacao label {
  font-size: 14px;
}

.button {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.button .submit {
  width: 70%;
  height: 40px;
  background-color: #2e3e46;
  border: none;
  color: #e1e1e1;
  margin: 30px 0;
  border-radius: 18px;
  cursor: pointer;
}

.btn_voltar {
  display: inline-block;
  width: 40%;
  height: 40px;
  background-color: #a11b1b;
  border: none;
  color: #e1e1e1;
  border-radius: 18px;
  text-decoration: none;
  text-align: center;
  line-height: 40px;
  cursor: pointer;
  font-family: Cambria, Cochin, Georgia, Times, "Times New Roman", serif;
  font-size: 13px;
}