index.html

  
  <div class="videoWrapper videoWrapper169 js-videoWrapper">
    <iframe class="videoIframe js-videoIframe" src="" frameborder="0" allowTransparency="true" allowfullscreen data-src="https://www.youtube.com/embed/hgzzLIa-93c?autoplay=1& modestbranding=1&rel=0&hl=sv"></iframe>
    <button class="videoPoster js-videoPoster" style="background-image:url(http://i2.wp.com/www.cgmeetup.net/home/wp-content/uploads/2015/05/Avengers-Age-of-Ultron-UI-Reel-1.jpg);">Play video</button>
  </div>
  
  <button onclick="videoStop()">external close button</button>
  

script.js

// poster frame click event
$(document).on('click','.js-videoPoster',function(ev) {
  ev.preventDefault();
  var $poster = $(this);
  var $wrapper = $poster.closest('.js-videoWrapper');
  videoPlay($wrapper);
});

// play the targeted video (and hide the poster frame)
function videoPlay($wrapper) {
  var $iframe = $wrapper.find('.js-videoIframe');
  var src = $iframe.data('src');
  // hide poster
  $wrapper.addClass('videoWrapperActive');
  // add iframe src in, starting the video
  $iframe.attr('src',src);
}

// stop the targeted/all videos (and re-instate the poster frames)
function videoStop($wrapper) {
  // if we're stopping all videos on page
  if (!$wrapper) {
    var $wrapper = $('.js-videoWrapper');
    var $iframe = $('.js-videoIframe');
  // if we're stopping a particular video
  } else {
    var $iframe = $wrapper.find('.js-videoIframe');
  }
  // reveal poster
  $wrapper.removeClass('videoWrapperActive');
  // remove youtube link, stopping the video from playing in the background
  $iframe.attr('src','');
}

style.scss

$color-button:       #fff;
$color-button-hover: #f00;

.videoWrapper {
  position: relative;
  width: 100%;
  height: 0;
  background-color: #000;
  &43 {
    padding-top: 75%;
  } 
  &169 {
    padding-top: 56%;
  } 
}
.videoIframe {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: transparent;
}
.videoPoster {
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  cursor: pointer;
  border: 0;
  outline: none;
  background-position: 50% 50%;
  background-size: 100% 100%;
  background-size: cover;
  text-indent: -999em;
  overflow: hidden;
  opacity: 1;
  -webkit-transition: opacity 800ms, height 0s;
  -moz-transition: opacity 800ms, height 0s;
  transition: opacity 800ms, height 0s;
  -webkit-transition-delay: 0s, 0s;
  -moz-transition-delay: 0s, 0s;
  transition-delay: 0s, 0s;
  &:before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 80px;
    height: 80px;
    margin: -40px 0 0 -40px;
    border: 5px solid $color-button;
    border-radius: 100%;
    -webkit-transition: border-color 300ms;
    -moz-transition: border-color 300ms;
    transition: border-color 300ms;
  }
  &:after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    margin: -20px 0 0 -10px;
    border-left: 40px solid $color-button;
    border-top: 25px solid transparent;
    border-bottom: 25px solid transparent;
    -webkit-transition: border-color 300ms;
    -moz-transition: border-color 300ms;
    transition: border-color 300ms;
  }
  &:hover,
  &:focus {
    &:before {
      border-color: $color-button-hover;
    }
    &:after {
      border-left-color: $color-button-hover;
    }
  }
  .videoWrapperActive & {
    opacity: 0;
    height: 0;
    -webkit-transition-delay: 0s, 800ms;
    -moz-transition-delay: 0s, 800ms;
    transition-delay: 0s, 800ms;
  }
}