<!doctype html>
<html>
<head>
<style>
body { margin:0; padding:48px; background:#0B1226; color:#F4E7D3;
font-family:Helvetica,Arial,sans-serif; }
h1 { margin:0 0 8px; font-size:15px; letter-spacing:.18em;
text-transform:uppercase; color:#8FA0C4; font-weight:normal; }
p.note { margin:0 0 28px; font-size:13px; color:#6C7A9C; }
.box { padding:16px 20px; margin:12px 0; background:#131E3D;
border:1px solid #22315C; border-radius:12px; font-size:15px; }
.box:hover { background:#F5A93C; color:#0B1226; border-color:#F5A93C; }
label { display:block; margin:14px 0; font-size:15px; }
details { margin:14px 0; font-size:15px; }
summary { padding:6px 0; }
#out { margin-top:24px; font-size:13px; color:#7FC3AC; }
</style>
</head>
<body>
<h1>Built-in behaviour</h1>
<p class="note">None of this is wired by hand — the engine owns it.</p>
<div class="box">hover me</div>
<label><input type="checkbox"> a checkbox that toggles</label>
<details>
<summary>a details element</summary>
<p>…that opens.</p>
</details>
<div id="out">keydown: none yet</div>
<script>
const out = document.querySelector("#out");
document.querySelector("body").addEventListener("keydown", (e) => {
out.textContent = "keydown: " + e.key;
});
</script>
</body>
</html>