16.js

function mouseShadow() {
    const hero = document.querySelector(".hero");
    const text = hero.querySelector("div");
    const walk = 300;

    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);
        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),
        ${xWalk}px ${yWalk * -1}px 0 rgba(0,255,0,0.7),
        ${xWalk * -1}px ${yWalk * -1}px 0 rgba(0,0,255,0.7)
        `;
    }
    hero.addEventListener("mousemove", shadow);
}
window.addEventListener("DOMContentLoaded", mouseShadow);