(--paper-input-container-invalid-color, --error-color);
      }

      .input-content.label-is-hidden ::content label,
      .input-content.label-is-hidden ::content .paper-input-label {
        visibility: hidden;
      }

      .input-content ::content input,
      .input-content ::content textarea,
      .input-content ::content iron-autogrow-textarea,
      .input-content ::content .paper-input-input {
        position: relative; /* to make a stacking context */
        outline: none;
        box-shadow