<div class="squatch-register">

  {{text}}

  <div class="form">
    {{#if firstName}}
      <input id="squatch-user-firstname" class="form-control" placeholder="First Name {{firstName}}">
    {{/if}}
    {{#if lastName}}
      <input id="squatch-user-lastname" class="form-control" placeholder="Last Name {{lastName}}">
    {{/if}}
    <input id="squatch-user-email" class="form-control" placeholder="Email (Required)"/>
    <button id="squatch-send-email" class="btn btn-primary">Continue</button>
  </div>
</div>

<div class="squatch-register">

  {{text}}

  <div class="form">
    <input id="squatch-user-firstname" class="form-control hide-{{firstName}}" placeholder="First Name">
    <input id="squatch-user-lastname" class="form-control hide-{{lastName}}" placeholder="Last Name">
    <input id="squatch-user-email" class="form-control" placeholder="Email (Required)"/>
    <button id="squatch-send-email" class="btn btn-primary">Continue</button>
  </div>
</div>

Add hide class to input fields
Add hide class to input fields
