On the subject of Extending Drupal 8

Apart from our mobile app development, we also do web development and maintenance. One of the sites that we maintain is the Cooler Crew web site, devoted to the St. Paul Winter Carnival Medallion Hunt, and similar treasure hunts in general (in the name of disclosure, the owner of this company is a long-time member of that group). We've been maintaining it for years, growing it from a massive collection of static pages, to something slightly database and template driven, to its current incarnation, built upon Drupal 6, and now Drupal 7.