styles.css

dialog {
  width: 100%;
  height: 100vh;
  display: flex;
}

form {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  width: 16rem;
  margin: auto;
  *+* { margin-top: 1rem; }

  header {
    p {
      font-size: .8rem;
      color: rgba(0,0,0,.5);
    }
  }

  footer {
    > *+* { margin-top: 0; }
    &:empty { display: none; }
    a {
      font-size: .62rem;
      color: #1e88e5;
    }
  }

  error- {
    font-size: .5rem;
    color: #d50000;
    line-height: 138%;
  }

  label {
    width: 100%;
  }

  input {
    width: 100%;
    padding: .5rem;
    padding-left: 0;
    font-size: 1rem;
    border-bottom: 2px solid rgba(0,0,0,.12);
    background: #fff;
    border-radius: 0;
    &:focus {
      border-bottom: 2px solid #4285f4;
    }
    &[readonly] {
      opacity: 0.5;
    }
  }

  button[type='submit'] {
    padding: .5rem;
    width: auto;
    font-size: .62rem;
    text-transform: uppercase;
    border: 1px solid rgba(0,0,0,.1);
    cursor: pointer;
    background-color: #1e88e5;
    color: #fff;
    transition: box-shadow .2s;
    border-radius: 2px;
    box-shadow: 0 1px 2px 0 rgba(0,0,0,.39);
    &:hover,
    &:focus {
      box-shadow: 0 2px 5px 0 rgba(0,0,0,.39);
    }
  }
}