If you have an existing Google Account you can use that to login to Ponder, just click the "Log in with Google" button on the login page.
You will be taken to the Google login page where you can enter your email and password.
Once you login, Google will ask you whether you want to authorize Ponder to create an account using your email address.
Click "Allow" and you'll be taken back to Ponder and logged in.
If you have already created a Ponder account and have a Google account with the same email address, you'll be able to login through either authorization option.