world-game/site/config/config.php

<?php

return [
    'debug'     => true,
    'languages' => true,

    'panel' => [
        'css'   => 'assets/css/custom-panel.css',
        'theme' => 'dark',
        'menu'  => require __DIR__ . '/menu.php',
    ],

    'thumbs' => require __DIR__ . '/thumbs.php',

    'routes' => [
        [
            'pattern' => ['(:any)/(:any)/download', 'en/(:any)/(:any)/download'],
            'method'  => 'POST',
            'action'  => function (string $parent, string $slug) {
                $page = kirby()->page($parent . '/' . $slug);
                if (!$page || $page->intendedTemplate()->name() !== 'white-paper') {
                    http_response_code(404);
                    header('Content-Type: application/json');
                    echo json_encode(['error' => 'Not found']);
                    exit;
                }
                // TODO: store/email form data ($kirby->request()->body())
                header('Content-Type: application/json');
                echo json_encode([
                    'success' => true,
                    'fileUrl' => $page->downloadFile()->toFile()?->url(),
                ]);
                exit;
            }
        ]
    ],
];