Developers who are still using the Google reCAPTCHA v1 API need to switch to the reCAPTCHA v2 API as the v1 API will shut down in March 2018. The service uses machine learning and its advanced risk analysis engine to figure out if users completing forms and other actions are humans or bots.
Google has long fielded complaints of sign-in requirements associated with Google Play Games. The Google+ requirement and multiple sign-ins required for multiple games has been a hotbed of frustration. Google announced the end of both requirements as part of a Google Play Games API model change.