Help. The width of input element does not resize when the viewport width changes.

<form action="index.html" method="POST">
    <fieldset>
        <legend class="heading">Contact Information</legend>
            <div class="form-wrapper">
                <label for="name" class="upper-label">Full Name</label><br>
                <input type="text" id="name" name="user_name" size="1" required><br>

                <label for="email" class="upper-label">Email Address</label><br>
                <input type="email" id="email" name="user_email" size="10" required><br>

                <label for="number" class="upper-label">Phone Number</label><br>
                <input type="tel" id="number" name="user_number" size="10"><br>

                <label for="address" class="upper-label">Street Address</label><br>
                <input type="text" id="address" name="user_address" size="10"><br>

                <label for="city" class="upper-label">City</label><br>
                <input type="text" id="city" name="user_city" size="10"><br>

                <label for="state" class="upper-label">State</label><br>
                <select name="user_state" id="state" size="10">
                    <option disabled selected value="">Choose State</option>
                    <option value="California">California</option>
                    <option value="Washington">Washington</option>
                </select><br>
                <label for="zip" class="upper-label">Zip Code</label><br>
                <input type="number" id="zip" name="user_zip" size="10"><br>
            </div>
    </fieldset>
    <hr class="thin-hr">
    <fieldset>
        <form action="index.html" method="POST">
            <legend>Newsletter</legend>
            <label>Select the newsletters you would like to receive</label>
            <input type="checkbox" id="htmlnews" name="htmlnames"><label for="htmlnews">HTML News</label><br>
            <input type="checkbox" id="cssnews" name="cssnews"><label for="cssnews">CSS News</label><br>
            <input type="checkbox" name="javascriptnews" id="javascriptnews"><label for="javascripts">Javascript News</label>  

            <label>Newsletter format</label>
            <input type="radio" class="html" name="html"><label for="html">HTML</label><br>
            <input type="radio" class="plaintext" name="plaintext"><label for="plaintext">Plain text</label><br>
            <label>Other topics you'd like to hear about</label><br>
            <textarea></textarea>
        </form>
    </fieldset>
</form>