script.js

const hero = document.querySelector('.hero');
const text = hero.querySelector('h1');
const walk = 30;

function shadow(e) {
    const { offsetWidth: width, offsetHeight: height } = hero;
    let { offsetX: x, offsetY: y } = e;

    if (this !== e.target) {
        x += e.target.offsetLeft;
        y += e.target.offsetTop;
    }

    const xWalk = Math.round((x / width) * walk - walk / 2);
    const yWalk = Math.round((y / height) * walk - walk / 2);

    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);