```css
/*
 * XolkerPark Public Form Styles
 * Version 1.0.0
 */

.xolkerpark-public-upload-form {
    border: 1px solid #e0e0e0;
    padding: 25px 30px;
    border-radius: 5px;
    background-color: #f9f9f9;
    max-width: 550px;
    margin: 2em auto;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
    box-shadow: 0 1px 2px rgba(0,0,0,0.07);
}

.xolkerpark-public-upload-form h2 {
    margin-top: 0;
    margin-bottom: 10px;
    font-size: 24px;
    color: #2271b1;
    text-align: center;
}

.xolkerpark-public-upload-form p {
    text-align: center;
    color: #555;
    font-size: 15px;
    margin-bottom: 25px;
}

.xolkerpark-public-upload-form .xp-form-field {
    margin-bottom: 20px;
}

.xolkerpark-public-upload-form label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #3c434a;
}

.xolkerpark-public-upload-form input[type="file"] {
    width: 100%;
    padding: 10px;
    border: 1px solid #c3c4c7;
    border-radius: 4px;
    background-color: #fff;
}

.xolkerpark-public-upload-form input[type="file"]::file-selector-button {
    background-color: #f0f0f1;
    border: 1px solid #c3c4c7;
    padding: 8px 12px;
    border-radius: 3px;
    cursor: pointer;
    margin-right: 10px;
    transition: background-color 0.2s;
}
.xolkerpark-public-upload-form input[type="file"]::file-selector-button:hover {
    background-color: #e0e0e0;
}

.xolkerpark-public-upload-form .xp-submit-btn {
    display: block;
    background-color: #2271b1;
    color: #fff;
    border: none;
    padding: 12px 20px;
    font-size: 16px;
    font-weight: 500;
    border-radius: 5px;
    cursor: pointer;
    width: 100%;
    text-align: center;
    transition: background-color 0.2s ease-in-out;
}

.xolkerpark-public-upload-form .xp-submit-btn:hover {
    background-color: #135e96;
}

.xolkerpark-public-upload-form .xp-error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
    padding: 12px;
    margin-bottom: 20px;
    border-radius: 4px;
    text-align: center;
}
```