script.js

const hero = document.querySelector('.hero');
const text = hero.querySelector('h1');
const walk = 100; //100px

function shadow(e) {
  const { offsetWidth: width, offsetHeight: height } = hero;
  let { offsetX: x, offsetY: y } = e;
  
  if (this !== e.target) {
    x = x + e.target.offsetLeft;
    y = y + e.target.offsetTop;
  }
  
  const xWalk = Math.round((x / width * walk) - (walk / 2));
  const yWalk = Math.round((y / height * walk) - (walk / 2));
  console.log('xWalk: ', xWalk, 'yWalk: ', yWalk);
  
  text.style.textShadow = `
    ${xWalk}px ${yWalk}px 0 rgba(255, 0,255,0.7),
    ${xWalk * -1}px ${yWalk}px 0 rgba(0,255,255,0.7),
    ${yWalk}px ${xWalk * -1}px 0 rgba(0,255,0,0.7),
    ${yWalk * -1}px ${xWalk}px 0 rgba(0,0,255,0.7)
  `;
  
}

hero.addEventListener('mousemove', shadow); 

/*
notes
text-shadow: h-shadow v-shadow blur-radius color|none|initial|inherit;
*/