Hothead Games is sort of building a new life for itself in the iOS space. The company has always been a downloadable game company, aiming for digital distribution for its titles rather than through the traditional retail stores. But up until last year, most of Hothead's work was for traditional consoles and PCs. After Hothead released Kard Combat and saw a lot of success with that freemium title, we saw the company change quite a bit. Nowadays, most of Hothead's work seems targeted at freemium casual games (the Big Win sports series has also been very popular for them), and the latest release, Zombie Ace, is no different.
On the face of it, Zombie Ace is very much "influenced" by Jetpack Joyride -- it's a one-button endless runner, where you tap the screen to move upwards as you fly along in a zombie-piloted plane. But there's a lot of new gameplay here as well: You can fight as you fly, throwing zombies and enemy planes. There are certain vehicles with trails you need to stay in, that will give you bonuses and other addons. And your plane is extremely upgradeable, providing a nice progression to the title that most endless runners don't have (you're flying across the country, basically, and you need to upgrade your plane enough to make it from Seattle to New York).
The whole game is very much driven by freemium purchases, which can get annoying (especially when the app asks you constantly to buy more IAP items, or sign up for TapJoy, or watch a commercial, or any of the other spammy stuff that are the model's worst offenders). But if you can make it past all of that crap, the game itself is a lot of fun, and there's a nice amount of polish on it as well. It's a little saddening to see Hothead move away from its premium history, and really depend so much on all of the spammy freemium tricks. But at least there is still some good gameplay in there, hidden under all of the IAP prompts.