title: sass: calculation between vh and px
body: <p>I have a slideshow on my landing screen that I want it to be fullscreen combined with a 70px height nav bar, I am trying to use sass so that I don't have to write javascript code for this, but </p>
  
  <pre><code>.slideshow{height:100vh-70px}
  </code></pre>
  
  <p>doesn't work. I don't know how sass calculates it, the CSS turns out to be </p>
  
  <pre><code>.slideshow{height:99.27083vh}
  </code></pre>
  
  <p>I did a quick search against this issue but couldn't find any useful information. So is this doable at all?</p>
  
  <p>And if no, is there anyway to do it without javascript?</p>