Firaxis and 2K Games have been busy with Apple's iOS platform. On top of Haunted Hollow, the studio behind XCOM: Enemy Unknown has released another free-to-play game for Apple's mobile devices. This one comes from Sid Meier and ventures to the days of World War I. Sid Meier's Ace Patrol is a turn-based strategy game that mixes in enough RPG elements to make you want to fly beyond the free-to-play horizon.
Ace Patrol puts you in the cockpit of the British air force during the Great War, where the skies are under contention between the Brits and the Germans. Battles play out over a hexagonal grid, with available moves determined by plane positions, pilot skills, and vehicle stats. Get close enough to an enemy fighter and you can fire on them, complete with fully animated cuts. Battles play out until one side is left standing. The iOS platform turns out to be a perfect forum for this type of strategy game, as moves are pulled off by tapping available moves. The learning curve is next to nil here, thanks to the simple controls and premise.
The solo campaign sees players completing a handful of missions with a variety of objectives. They include protecting points of interest, taking out German convoys, and escorting allies. Inevitably, most missions will turn into all-out dogfights, with the winner being the last team standing. Later missions can be purchased, but don't feel overly expensive. Other campaigns (German, French, and American) are also behind a low price tag. There isn't much difference between the varying campaigns, each with similar objectives. However, anyone that enjoys the action and the field layouts will likely appreciate the extra replay value. Just be forewarned that you'll only be able to progress so far before crashing into the paywall.
Ace Patrol also sprinkles in a good amount of RPG elements that make it surprisingly deep. Successful runs will earn upgrades for your pilot and plane, as well as unlock other planes. Players will need to be selective with their pilots and choose them based on who needs to be upgraded and whose unique abilities will best suit the mission. Keeping an evenly-balanced fighting force is beneficial, since many of the campaign's latter missions will require use of all available pilots.
In-app purchases don't ground Ace Patrol too much, though there are a couple of annoying ones. Most notably, failing a mission in enemy territory will result in your pilot getting captured and the only way to free him is to fork over real money. Aside from that irritating instance, IAP's are reasonably priced, given how much fun the overall experience feels, and there is an option to buy the full game in one lump sum, rather than getting nickel-and-dimed.
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As is the case with Haunted Hollow, Ace Patrol's greatest strength lies in its multiplayer. Local multiplayer allows for two friends to play against each other on the same device. Objectives are randomized and some tend to give more of an advantage to one side than another. For example, one scenario saw one side get an AI surveillance plane, while the opponent had to shoot it down. Both sides took their two planes and started combating each other, only to forget about the surveillance plane. The AI plane completed its mission and the second player wound up winning, as the human battle was still going. Despite these occasional balance issues, multiplayer is one of Ace Patrol's better features. Ace Patrol also features online multiplayer, but it doesn't appear to have left the runway, as it was not functioning at the time of this review.
Firaxis continues to nail down the strategy genre with Sid Meier's Ace Patrol. 2K also continues to demonstrate positive ways to execute the free-to-play model, offering plenty of incentive to play a decently-priced campaign without shutting out players that simply want to take to the skies without laying down a dime. 
This Sid Meier's Ace Patrol review was based on a the free-to-play version of the game played on a third-generation iPad. The reviewer purchased the German, American, and French Triple-Pack for $3.99. The game is now available in the App Store.