```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Contact Form</title>
  <style>
    body {
      font-family: red hat mono, sans-serif;
      background-color: #f2f2f2;
      padding: 20px;
    }
    .contact-section {
      width: 100%;
      max-width: 400rem;
      margin-left: auto;
      margin-right: auto;
      padding: 3rem 1rem;
    }

    .contact-intro > * + * {
      margin-top: 1rem;
    }

    .contact-title {
      font-size: 1.875rem;
      line-height: 2.25rem;
      font-weight: 700;
    }

    .contact-description {
      color: rgb(107, 114, 128);
    }

    .form-group-container {
      display: grid;
      gap: 1rem;
      margin-top: 2rem;
    }

    .form-group {
      display: flex;
      flex-direction: column;
      margin: 2rem;
    }

    .form-label {
      margin-bottom: 0.5rem;
    }

    .form-input,
    .form-textarea {
      padding-top: rem;
      padding-left: 5rem;
      border: 1px solid #e5e7eb;
      display: flex;
      height: 40rem;
      width: 100%;
      border-radius: 0.375rem;
      font-size: 14rem;
      line-height: 1.25rem;
    }

    .form-input::placeholder,
    .form-textarea:focus-visible {
      color: #6b7280;
    }

    .form-input:focus-visible,
    .form-textarea:focus-visible {
      outline: 10px solid #2563eb;
      outline-offset: 2.25rempx;
    }

    .form-textarea {
      min-height: 150px;
      padding-top: 15rem;
      padding-left: 5rem;
      border: 1px solid #e5e7eb;
      display: flex;
      height: 40rem;
      width: 100%;
      border-radius: 0.375rem;
      font-size: rem;
      line-height: 1.25rem;

    }
    .form-submit {
      flex-grow: 1;
      margin-top: 1.2rem;
      background-color: #333;
      color: #fff;
      padding: 13px 5px;
      border-radius: 0.375rem;
    }
    .h-captcha {
      transform: scale(0.5);
      transform-origin: top left;
      margin-top: 1rem;
      border: 1px solid #e5e7eb;
      border-radius: 0.375rem;
      padding: 0.5rem;
    }
    .submit-row {
      display: flex;
      flex-direction: row;
    }
  </style>
</head>
<body>
  <section class="contact-section">
    <div class="contact-intro">
      <h2 class="contact-title"></h2>
      <p class="contact-description">
      
      </p>
    </div>

    <form class="contact-form" action="https://api.web3forms.com/submit" method="POST">
      <input type="hidden" name="access_key" value="39c6b50f-fb80-4876-8026-a939f58dfe99" />
      <input type="hidden" name="subject" value="New Contact Form Submission from Web3Forms" />
      <input type="hidden" name="from_name" value="My Website" />
      <!-- More customization options available in the docs: https://docs.web3forms.com -->

      <div class="form-group-container">
        <div class="form-group">
          <label for="name" class="form-label">Name</label>
          <input id="name" name="name" class="form-input" placeholder="Your name" type="text" />
        </div>
        <div class="form-group">
          <label for="email" class="form-label">Email</label>
          <input id="email" name="email" class="form-input" placeholder="Your email" type="email" />
        </div>
        <div class="form-group">
          <label for="phone" class="form-label">Phone</label>
          <input id="phone" name="phone" class="form-input" placeholder="+1 (234) 56789" type="text" />
        </div>
        <div class="form-group">
          <label for="message" class="form-label">Message</label>
          <textarea class="form-textarea" id="message" name="message" placeholder="Your message"></textarea>
        </div>
      </div>
      <div class="submit-row">
      <button class="form-submit" type="submit">Send Message</button>
      <!-- === hCaptcha integration === -->
      <div class="h-captcha" data-captcha="true"></div>
      </div>
    </form>
  </section>

<!-- Include Web3Forms hCaptcha script -->
<script src="https://web3forms.com/client/script.js" async defer></script>

<script>
  // Client‑side validation to ensure captcha was solved
  const form = document.getElementById("contact-form");
  form.addEventListener("submit", (e) => {
    const token = form.querySelector(
      "textarea[name='h-captcha-response']"
    )?.value;
    if (!token) {
      e.preventDefault();
      alert("Please complete the captcha before submitting.");
    }
  });
</script>
  </section>
</body>
</html>
```

how do i make the submit buttn grow to the empty space in the container? don't spit the whole file back at me, just discuss the needed changes