text: (function flexible (window, document) {
      var docEl = document.documentElement
      var dpr = window.devicePixelRatio || 1
    
      // adjust body font size
      function setBodyFontSize () {
        if (document.body) {
          document.body.style.fontSize = (12 * dpr) + 'px'
        }
        else {
          document.addEventListener('DOMContentLoaded', setBodyFontSize)
        }
      }
      setBodyFontSize();
    
      // set 1rem = viewWidth / 10
      function setRemUnit () {
        var rem = docEl.clientWidth / 10
        docEl.style.fontSize = rem + 'px'
      }
    
      setRemUnit()
    
      // reset rem unit on page resize
      window.addEventListener('resize', setRemUnit)
      window.addEventListener('pageshow', function (e) {
        if (e.persisted) {
          setRemUnit()
        }
      })
    
      // detect 0.5px supports
      if (dpr >= 2) {
        var fakeBody = document.createElement('body')
        var testElement = document.createElement('div')
        testElement.style.border = '.5px solid transparent'
        fakeBody.appendChild(testElement)
        docEl.appendChild(fakeBody)
        if (testElement.offsetHeight === 1) {
          docEl.classList.add('hairlines')
        }
        docEl.removeChild(fakeBody)
      }
    }(window, document))