* {
  box-sizing: border-box;
  font-family: Arial, Helvetica, sans-serif;
}

main {
  width: 100%;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

form {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  justify-content: space-between;
  gap: 16px;
  max-height: 150px;
  height: 100%;
}

form > button {
  width: 100%;
  height: 3rem;
  font-size: 1.5rem;
  font-weight: 600;
  border: 1px solid black;
  cursor: pointer;
}

.two-factor-group {
  display: flex;
  align-items: stretch;
  gap: 16px;
  border: none;
  padding: 0;
}

.two-factor-input {
  border: 2px solid black;
  width: 3rem;
  height: 3.5rem;
  font-size: 1.5rem;
  font-weight: 600;
  text-align: center;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input:required:invalid {
  border: none;
  outline: 2px solid red;
}

/* Firefox */
input[type=number] {
  -moz-appearance: textfield;
}