Just add the class .form to your form and take a break.
<form class="form">
<fieldset>
<legend>Text fields</legend>
<ol>
<li>
<label for="text-field">Text Field 100%</label>
<input type="text" id="text-field" placeholder="Text field 100%"/>
</li>
<li>
<label for="url-field">URL Field</label>
<input type="url" id="url-field" />
</li>
<li>
<label for="email-field">Email Field</label>
<input type="email" id="email-field" placeholder="email" />
</li>
<li>
<label for="Password-field">Password Field</label>
<input type="password" id="Password-field" />
</li>
<li>
<label for="color-field">Color Field</label>
<input type="color" id="color-field" />
</li>
<li>
<label for="text-area">Textarea</label>
<textarea id="text-area"></textarea>
</li>
</ol>
</fieldset>
<fieldset>
<legend>Details</legend>
<details open>
<summary>Details opened. <em>Click arrow to close it</em></summary>
<p>This is details text.</p>
<p>This is details text.</p>
<p>This is details text.</p>
</details>
<details>
<summary>Details closed. <em>Click arrow to open it</em></summary>
<p class="h3">HELLO! YOU HAVE OPENED DETAILS!</p>
</details>
</fieldset>
</form>