<div id="tracker">
	<!-- I found that mouse tracking doesn't work well with an SVG; the browser changes the window position when hovering over the SVG. The solution was to instead create an invisible element (this one) over the top of the page that tracks the movements, and to use JS to fake the other hover effects.	 -->
</div>

<div id="text">
	<p>Move your mouse to <span class="highlight">play&nbsp;with&nbsp;the&nbsp;cat.</span></p>
	<p>Click the button to <span class="highlight">get&nbsp;back&nbsp;to&nbsp;work.</span></p>
</div>

<main>
	<button id="target">
		Stop<br />playing
		<img id="cursor" src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/240751/mac-osx-arrow-cursor.png" alt="">
	</button>
	<!-- SVG created with Affinity Designer -->
	<svg id="Cat" width="100%" height="100%" viewBox="-80 0 200 199" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" xmlns:serif="http://www.serif.com/" style="fill-rule:evenodd;clip-rule:evenodd;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:1.5;"><rect id="Artboard1" x="0" y="0" width="104.557" height="198.931" style="fill:none;"/><path id="Body" d="M21.605,75.113c2.759,17.247 -5.015,37.589 -6.724,59.831c-1.71,22.241 0.016,62.893 30.999,62.893c0.946,0 1.873,-0.075 2.784,-0.058c34.988,0.655 40.376,-21.661 35.482,-45.091c-5.047,-24.167 -22.908,-35.604 -24.535,-74.071c-1.627,-38.467 -42.011,-28.548 -38.006,-3.504Z"/><path id="Head-main" serif:id="Head main" d="M60.011,27.971c4.811,-11.449 12.131,-28.237 13.564,-27.938c2.015,0.422 6.111,41.652 6.688,47.562c0.027,0.233 0.049,0.467 0.068,0.702l0,0.001l0,0c0.043,0.537 -0.064,1.099 0.064,1.639c4.823,20.225 -6.8,28.68 -39.075,28.68c-32.275,0 -43.354,-10.637 -39.075,-28.68c0.128,-0.541 0.022,-1.102 0.064,-1.64l-0.064,0.001c0,0 5.295,-47.81 7.466,-48.265c1.425,-0.298 8.674,16.308 13.486,27.752c5.404,-1.544 11.553,-2.337 18.078,-2.337c6.783,0 13.168,0.856 18.736,2.523Z"/><g id="Left-eye" serif:id="Left eye"><circle cx="17.962" cy="55.289" r="11.393" style="fill:#fff;"/><g id="Left-eye-pupil" serif:id="Left eye pupil"><circle cx="16.068" cy="53.396" r="9.499"/><circle cx="13.934" cy="48.382" r="2.134" style="fill:#fff;"/></g></g><g id="Right-eye" serif:id="Right eye"><circle cx="64.679" cy="55.289" r="11.393" style="fill:#fff;"/><g id="Right-eye-pupil" serif:id="Right eye pupil"><circle cx="61.777" cy="53.396" r="9.499"/><circle cx="59.643" cy="48.382" r="2.134" style="fill:#fff;"/></g></g><path id="Tail" d="M80.004,178.286c-0.131,0.058 12.828,-18.528 5.347,-42.302c-7.482,-23.774 2.767,-37.597 13.789,-42.67" style="fill:none;stroke:#000;stroke-width:8px;"/><path id="Paw" d="M29.354,99.466c-0.04,-20.799 15.679,-43.724 6.404,-62.895" style="fill:none;stroke:#000;stroke-width:10px;"/></svg>
</main>
@import url('https://fonts.googleapis.com/css?family=Luckiest+Guy&display=swap');

$accent: #7BA7BC;
$paw: 1rem;
$black: #333;

*, *:before, *:after {
	box-sizing: inherit;
	font-family: inherit;
	position: inherit;
}

body {
	background: #feeeed /* me */;
	margin: 0;
	box-sizing: border-box;
	position: relative;
	display: grid;
	place-items: center;
	min-height: 100vh;
	font-size: 18px;
	font-family: 'Luckiest Guy', sans-serif;
	color: $accent;
	grid-template-rows: 1fr 4fr;
	overflow: hidden;
	
	#tracker {
		width: 100vw;
		height: 100vh;
		position: fixed;
		top: 0;
		left: 0;
		z-index: 5;
	}
}

p {
	font-size:calc(1.1rem + 1vw);
	line-height: 1.4em;
	margin: 0;
	text-align: center;
	color: $black;
	
	.highlight {
		color: $accent;
	}
}

main {
	width: 100%;
	max-width: 22rem;
	display: flex;
	align-items: center;
	
	button {
		padding: .5em .8em .3em;
		font-weight: bold;
		background: $accent;
		color: #fff;
		border-radius: 5rem;
		margin-right: -10rem;
		cursor: none;
		border: none;
		font-size: 1.5rem;
		line-height: 1;
		letter-spacing: .05em;
		color: $black;
		border: .2rem solid $black;
		transition: margin .05s ease;
		transform-origin: center;
		
		&:focus, &:hover, &:active {
			outline: none;
			border: .3rem solid $black;
		}
	}
	
	#cursor {
		position: absolute;
		width: 16px;
		left: 50%;
		top: 50%;
		z-index: -2;
		transform-origin: center;
		opacity: 0;
		
		&.swatted {
			opacity: 1;
			animation: swatted .15s ease-out;
		}
	}
	
	#Cat {
		transform-origin: bottom center;
		animation: tail 7s infinite alternate;
		z-index: 0;
		pointer-events: none;
	}
	
	#Tail {
		transform-origin: bottom;
		animation: tail 2s ease infinite alternate;
	}
	
	#Paw {
		transform-origin: 16% 53%;
		transform: rotate(-185deg);
		filter: blur(22px);
		transition: all .2s;
		
		&.ready-to-swat {
			transform: rotate(-56deg);
		}
	}
	
	.swat {
		animation: swat .2s;
	}
	
	#Left-eye-pupil, #right-eye-pupil {
		transform-origin: center;
	}
	
	#Left-eye, #Right-eye {
		animation: blink 8s infinite alternate;
		transform-origin: 50% 26%;
	}
}

@keyframes tail {
	0% {
		transform: rotate(0deg);
	}
	27% {
		transform: rotate(2deg);
	}
	69% {
		transform: rotate(-2deg);
	}
	100% {
		transform: rotate(0deg);
	}
}

@keyframes swat {
	0% {
		transform: rotate(-20deg) scale(1.2);
	}
	
	25% {
		transform: rotate(-82.5deg) scale(1.2);
	}
	
	50% {
		transform: rotate(-185deg) scale(1.2);
	}
	51% {
		transform: rotate(-20deg) scale(1.2);
	}
	
	75.5% {
		transform: rotate(-82.5deg) scale(1.2);
	}
	
	100% {
		transform: rotate(-185deg) scale(1.2);
	}
}

@keyframes blink {
	0% {
		transform: scaleY(1);
	}
	39% {
		transform: scaleY(1);
	}
	40% {
		transform: scaleY(0);
	}
	41% {
		transform: scaleY(1);
	}
	69% {
		transform: scaleY(1);
	}
	70% {
		transform: scaleY(0);
	}
	71% {
		transform: scaleY(1);
	}
	100% {
		transform: scaleY(1);
	}
}

@keyframes swatted {
	0% {
		opacity: 1;
		transform: scale(1) translate(0, 0) rotate(0deg);
	}
	100% {
		opacity: 1;
		transform: scale(3) translate(-15vw, 20vh) rotate(1080deg);
	}
}
View Compiled
//Just a shorthand since there's a lot of selectors
const get = arg => document.querySelector(arg);

//Select all the things
const tracker = get('#tracker');
const button = get('button');
const paw = get('#Paw');
const tail = get('#Tail');
const leftEye = get('#Left-eye-pupil');
const rightEye = get('#Right-eye-pupil');
const cat = get('svg');
const cursor = get('#cursor');

//What happens when mousing over the button
const mouseOver = () => {
	paw.style.transform = 'rotate(-185deg)';
	if(!paw.classList.value.includes('swat')) {
		paw.classList.add('swat');
		cursor.classList.add('swatted');
		document.body.style.cursor = 'none';
		cat.style.animation = 'none';
		tail.style.animation = 'none';
		document.body.style.cursor = 'none';
		button.style.marginRight = '-11rem';
	}
}

//What happens when mousing out from the button
const mouseOut = () => {
	if(paw.classList.value.includes('swat')) {
		paw.classList.remove('swat');
		cursor.classList.remove('swatted');
		cat.style.animation = 'tail 7s infinite alternate';
		tail.style.animation = 'tail 2s ease infinite alternate';
		document.body.style.cursor = 'unset';
		button.style.marginRight = '-10rem';
	}
}

//What happens when we're near the button
const mouseNear = (coords, x, y) => {
	const minY = coords.y - coords.height;
	const maxY = coords.y + (coords.height * 2);
	const minX = coords.x - coords.width;
	const maxX = coords.x + (coords.width * 2);
	const zeroX = (maxX + minX) / 2;
	const zeroY = (maxY + minY) / 2;
	paw.style.transform = `rotate(-${60 / (zeroX + zeroY) * (x + y)}deg)`;
}

//Boolean; whether the cursor is over the button
const overTheButton = (coords, x, y) => {
	return y >= coords.y && y <= coords.y + coords.height && x >= coords.x && x <= coords.x + coords.width;
}

//Boolean; whether the cursor is near the button
const nearTheButton = (coords, x, y) => {
	return y >= coords.y - (coords.height * 2) && y <= coords.y + (coords.height * 3) && x >= coords.x - coords.width && x <= coords.x + (coords.width * 2)
}


//The actual event listener that tracks the mouse (see the HTML note)
tracker.addEventListener('mousemove', e => {
	const btnCoords = button.getBoundingClientRect();
	const x = e.offsetX;
	const y = e.offsetY;
	const windowHeight = window.innerHeight;
	const windowWidth = window.innerWidth;
	const max = 3;
	
	//Execute the proper function(s) from above based on cursor placement
	if(overTheButton(btnCoords, x, y)) {
		mouseOver();
	} else { 
		mouseOut();
		if (nearTheButton(btnCoords, x, y)){
			mouseNear(btnCoords, x, y);
		} else {
			paw.style.transform = 'rotate(-185deg)';
		}
	}
	
	//Eye movement
	[leftEye, rightEye].forEach(eye => {
		eye.style.transform = 
		`translate(
			${max / (windowWidth / x)}%,
			${max / (windowHeight / y)}%
		)`;
	});
});
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