js代码

<script>
var stage = document.querySelector('.stage');
var background = document.querySelector('.background');

var rotation = 0;

document.querySelector('.button_prev').
addEventListener('click', function () {return applyStyles(rotation += 90);});

document.querySelector('.button_next').
addEventListener('click', function () {return applyStyles(rotation -= 90);});

function applyStyles() {
  background.style.filter = 'hue-rotate(' + rotation + 'deg)';
  stage.style.transform = 'rotateZ(' + rotation + 'deg)';
}</script>