Why tower defence never really goes out of style

Tower defence has been declared stale roughly every year since it appeared, and every year a new one shows up and eats everyone's weekend. There's something durable about the formula that's worth understanding.

At its heart it's a puzzle that plays itself out. You make your decisions, then watch them succeed or fail. That mix of control and spectacle is deeply satisfying, and it maps perfectly onto touchscreens.

The genre also scales cleanly. A tower defence game can be a two-minute casual snack or a twenty-minute strategic grind depending on how it's tuned, which is why it lives so comfortably on phones.

Modern entries keep it fresh by layering on economy, hero units, and roguelike runs. The core stays the same, but the flavour keeps changing. That's the mark of a genre that isn't going anywhere.