To play a game without a form, you can disable mandatory authentication

To do this, go to your campaign settings > General Settings > Advanced Settings

To do this, go to the edition of your campaign.

Click on the "Settings" button:

Then go to the Advanced Settings > Sessions section and desactivate the "Authentication required" toggle

Be careful, you will not be able to limit the participation if you disable the authentication because the limitation is done via the e-mail address.