There are tons of tower defense games on the App Store, and for good reason-- The touch interface and fairly slow-paced gameplay just works fantastic on iOS devices. I have quite a few favorites in the genre, but Origin8's Sentinel 2: Earth Defense [Free] is always on the top of any list of tower defense games I recommend. There is just so much I like about this game which I explained in my review.

In a nutshell, Sentinel 2 has great graphics, good sound effects, a nice variety in both towers and enemies, and the inclusion of both repair drones as well as different destructible barriers to defend really adds an interesting layer of strategy to the game. There are also mega weapons that are fired from your orbiting space ship that slowly recharge over time, my personal favorite being a massive orbital laser strike that destroys anything it comes in contact with. The best thing about Sentinel 2, at least in my opinion, is how well the game is balanced.

There doesn't seem to be any "right" way to beat the included levels, as quite a wide variety of different tower constructing and upgrading strategies all seem to work. This makes the game a lot more fun than a lot of other tower defenders which often seem to be games of how intelligently you can manage your resources to ramp up to whatever the fully upgraded ultimate tower is that kills everything in one hit-- Allowing you to just put your phone down and wait for all the waves to just die to your defenses and for the next level to start.

If you even have a vague interest in tower defense games, or even have never played one before, you should download Sentinel 2 while it's free. If you miss the window of the freebie promotion, I'd even recommend buying it.

  • http://www.robotplague.com robotplague

    Totally skipped this when it came out always with the intention of getting it at some point. Stoked to get it for free now.

  • http://www.robotplague.com robotplague

    Totally skipped this when it came out always with the intention of getting it at some point. Stoked to get it for free now.

  • PahnCrd

    I played he crap out of this game. At $0 it is a no brainer for anyone even slightly interested in tower defense.

  • PahnCrd

    I played he crap out of this game. At $0 it is a no brainer for anyone even slightly interested in tower defense.

  • Mister Mumbles

    Should I feel guilty about now having picked up both Sentinel games for free? *blush* Great games of tower defense.

    • Remon

      You can releave yourself of that guild a little bit by getting the extra levels in the game. That's what I did after getting the 2 games for free and it help a little :)

      Great games! Still looks great on the iPad when enlarged.

  • Mister Mumbles

    Should I feel guilty about now having picked up both Sentinel games for free? *blush* Great games of tower defense.

    • Remon

      You can releave yourself of that guild a little bit by getting the extra levels in the game. That's what I did after getting the 2 games for free and it help a little :)

      Great games! Still looks great on the iPad when enlarged.

  • thebleeptruth

    How i wish they'd make Space Station free for a day. I already own both Sentinel games.

  • thebleeptruth

    How i wish they'd make Space Station free for a day. I already own both Sentinel games.

  • K Mellars

    Should say Only Free if you agree to use Open Feint if not forget it

    • http://origin8.com Repair Drone

      Speaking as the person who pressed the button in iTunes Connect, I can assure you that it's free without qualification. The promotion is in association with OpenFeint, but there's absolutely no way to set up the situation that you're describing. It's either free or it ain't :)

  • K Mellars

    Should say Only Free if you agree to use Open Feint if not forget it

    • http://origin8.com Repair Drone

      Speaking as the person who pressed the button in iTunes Connect, I can assure you that it's free without qualification. The promotion is in association with OpenFeint, but there's absolutely no way to set up the situation that you're describing. It's either free or it ain't :)

  • Asolja

    Yep Free only if using open feint

  • Asolja

    Yep Free only if using open feint

  • iHuff

    Love this game - last Tower Defence standing on my touch after all the others have withered away.

  • iHuff

    Love this game - last Tower Defence standing on my touch after all the others have withered away.

  • Leonick

    Nice this one is a really good tower defense.
    The towers where much better in the original though, graphically that is, they acrually changed their look to indicate you upgraded instead of you switching a light on at its base :P

  • Leonick

    Nice this one is a really good tower defense.
    The towers where much better in the original though, graphically that is, they acrually changed their look to indicate you upgraded instead of you switching a light on at its base :P

  • WeaponOfChoice

    The maximum upgrade of the tower switches to a completely new version...the lights are only the steps to max power :)

  • WeaponOfChoice

    The maximum upgrade of the tower switches to a completely new version...the lights are only the steps to max power :)