<div class="wrapper">
<button class="button1">
<i></i><i></i>
<span>button</span>
</button>
</div>
<script>
let btn = document.querySelector('button');
btn.addEventListener('mousemove', e => {
let rect = e.target.getBoundingClientRect();
let x = e.clientX *2 - rect.left;
btn.style.setProperty('--x', x + 'deg');
})
</script>