<div class="crossbars crossbars__horizontal"></div>
<div class="crossbars crossbars__vertical"></div>

html, 
body {
	width: 100%;
	height: 100%;
}

.crossbars {
	position: fixed;
	top: 0;
	left: 0;
	pointer-events: 0;
	background-color: #000;
	z-index: 100; // increase if needs be
  
	&__horizontal {
		width: 100%;
		height: 2px;
	}

	&__vertical {
		width: 2px;
		height: 100%;
	}
}

const crossbar__horizontal = document.querySelector('.crossbars__horizontal');
const crossbar__vertical = document.querySelector('.crossbars__vertical');
const pos = { x: window.innerWidth / 2, y: window.innerHeight / 2 };
const mouse = { x: pos.x, y: pos.y };
const speed = 0.8; // 0 to 1.

const ySet = gsap.quickSetter(crossbar__horizontal, 'y', 'px');
const xSet = gsap.quickSetter(crossbar__vertical, 'x', 'px');

window.addEventListener('mousemove', (e) => {
	mouse.x = e.x;
	mouse.y = e.y;
});

gsap.ticker.add(() => {
	const dt = 1.0 - Math.pow(1.0 - speed, gsap.ticker.deltaRatio());
	pos.x += (mouse.x - pos.x) * dt;
	pos.y += (mouse.y - pos.y) * dt;
	xSet(pos.x);
	ySet(pos.y);
});