.signup {
  display: flex;
  margin: 20px 0 0;
}

.signup input,
.signup button {
  height: 50px;
  border: 1px solid currentColor;
  background: black;
  font-size: 16px;
  font-family: inherit;
  color: white;
  padding: 0 16px;
}

.signup input {
  flex: 1;
  max-width: 400px;
  margin-right: 16px;
}

.signup button {
  flex: 0;
}