ButtonLang.html

<style>
code {
	background-color: lightgray;
	padding: 2px;
	border-radius: 3px;
	border: 1px gray;
}

li {
	margin-bottom: 3px;
}
</style>

<p>Welcome to my esolang ButtonLang!</p>

<button onclick="up()">+</button>
<p id="number">0</p>
<button onclick="down()">-</button>

<p>In ButtonLang, you are both the program and the interpreter. You may press the buttons to execute the ButtonLang program you want to.</p>

<p>Commands:</p>

<ul>
	<li><code>+</code> Increment the accumulator.</li>
	<li><code>-</code> Decrement the accumulator.</li>
</ul>

<script>
number = document.getElementById("number");

function up() {
	number.innerHTML = (parseInt(number.innerHTML) + 1).toString();
}

function down() {
	number.innerHTML = (parseInt(number.innerHTML) - 1).toString();
}
</script>