Let's learn a new concept which explains how variables keep track of things like adding or removing dollars from a wallet.

<html>
<head>
<style>
button {
background-color: darkBlue; /* Green */
border: none;
border-radius: 8px;
color: white;
text-align: center;
text-decoration: none;
display: inline-block;
font-size: 14px;
padding: 6px 12px;  
margin: 0 12px 0 0;
}
</style>
</head>
<body>
<h1>Wallet: <strong>$<span id="amount">15</span></strong></h1>
<button onclick="add()">Add $1</button>
<button onclick="remove()">Remove $1</button>
<script>
var wallet = 15;
let amountCounter = document.getElementById('amount');
function add() { wallet += 1; amountCounter.innerHTML = wallet; }
function remove() { wallet -= 1; amountCounter.innerHTML = wallet; }
</script>
</body>
</html>]]>