static/usage/v8/button/shape/demo.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Button</title>
    <link rel="stylesheet" href="../../common.css" />
    <script src="../../common.js"></script>
    <script type="module" src="https://cdn.jsdelivr.net/npm/@ionic/core@next/dist/ionic/ionic.esm.js"></script>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@ionic/core@next/css/ionic.bundle.css" />
  </head>

  <body>
    <ion-app>
      <ion-content>
        <div class="container">
          <ion-button>Default</ion-button>
          <ion-button shape="round">Round</ion-button>
          <ion-button>
            <ion-icon slot="icon-only" name="heart"></ion-icon>
          </ion-button>
          <ion-button shape="round">
            <ion-icon slot="icon-only" name="heart"></ion-icon>
          </ion-button>
        </div>
      </ion-content>
    </ion-app>
  </body>
</html>