These three features come with a PRO key, in the same plugin. Without PRO they are shown locked, so you can see what they do.
Split testing:
On the Display tab, under Split Testing, turn on Split test this campaign. Percent who see version B can be set from 5 to 95, and 50 is the place to start. Version B is an override rather than a second campaign: fill in only what should be different (headline, sub-line, button text, button link, background or button colour) and anything you leave blank stays the same as version A. Each visitor keeps the same version every time they come back, so the result stays honest.
The Campaigns list shows a note under the campaign name. It judges on conversion rate, never on raw conversions, and it says nothing until both versions have 100 views. When the two rates are within half a percentage point it says too close to call.
Geo targeting:
On the Targeting tab, under Geo Targeting, choose Every country (the default, where Engage never looks the visitor up), Only the countries below, or Everywhere except the countries below. Type a country name and click to add it. A visitor whose country cannot be worked out always sees the campaign, so a failed lookup never costs you a subscriber. The country is worked out in the visitor's browser rather than baked into the page, so it works with page caching.
Spin To Win:
Spin To Win is a popup type where the visitor enters their email and spins a prize wheel. On the Content tab you set two to eight segments, each with a label, a weight and an optional coupon code. A segment with no code is a losing one. Weights are relative, so they never have to add up to 100, and the panel prints the real chance beside each segment. A weight of 0 puts a segment on the wheel that can never be won.
The winner is drawn on your server, and only then does the wheel spin to that segment. Coupon codes and the odds are not sent to the browser, so they cannot be read out of the page source. Set the campaign to show Once, ever on the Display tab so nobody spins twice, and start from the Spin To Win Wheel template if you like.