A Pen by trieu truong

    <div class="calculator">
  <p>FreeCodeCalc</p>
</div>
<div class="calc-row">
   <div class="screen">
     012345
  </div>
</div>
  <div class="calc-row">
    <div class="button">
      C
    </div>
    <div class="button">
      CE
    </div>
    <div class="button backspace">
      back
    </div>
    <div class="button plus-minus">
      +/-
    </div>
    <div class="button">%</div>
  </div>
  <div class="calc-row">
    <div class="button">7</div><div      class="button">8</div><div class="button">9</div><div class="button divice">/</div><div class="button root">sqrt</div>
  </div> 
  <div class="calc-row">
    <div class="button">4</div><div class="button">5</div><div class="button">6</div><div class="button multiply">*</div><div class="button inverse">1/x</div>
  </div>
   <div class="calc-row">
    <div class="button">1</div><div class="button">2</div><div class="button">3</div><div class="button">-</div><div class="button pi">pi</div>
  </div>
  
  <div class="calc-row">
    <div class="button zero">0<div><div class="button decimal">.</div><div class="button">+</div><div class="button equal">=</div>
</div>
</div>