world-game/site/templates/play.json.php

<?php

$specificData = [
  'games' => $page->children()->listed()->map(function($game) {
    return [
      'title'            => $game->title()->value(),
      'slug'             => $game->slug(),
      'lettering'        => $game->lettering()->toFile()?->url(),
      'description'      => $game->description()->value(),
      'thumbnail'        => $game->thumbnail()->toFile()?->url(),
      'thumbnailSrcset'  => $game->thumbnail()->toFile()?->srcset('thumbnail'),
      'thumbnailWebp'    => $game->thumbnail()->toFile()?->srcset('thumbnail-webp'),
      'backgroundColor'  => $game->backgroundColor()->value() ?: null,
      'preview'          => $game->preview()->toFile()?->url(),
      'playLink'         => $game->playLink()->value() ?: null,
    ];
  })->values()
];

$pageData = array_merge($genericData, $specificData);

header('Content-Type: application/json');
echo json_encode($pageData);