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Sentinel 2: Earth Defense

Sentinel 2: Earth Defense from Origin8 is the sequel to the much-acclaimed Sentinel, now called now called Sentinel: Mars Defense and originally reviewed by Chris J here (let’s just call them S1 and S2 hereafter).  The story goes that despite your valiant efforts defending the Mars mining colony you ultimately failed, the base was completely overrun, everyone died and now the aliens have their belligerent eyes fixed on another target…Earth.  Pushing aside your prior job performance, top brass has again entrusted you with the job of defending a planet…just this time it’s your own (no pressure).  You’ve got a little something extra to bring to the party this time though in the form of 4 orbital attacks from the spaceship Sentinel, 2 new barrier types and 1 new drone (more on this later).  Add 4 maps, sprinkle in a new boss alien plus a new mission mode and you have yourself a sequel.

If you aren’t familiar with the tower defense (TD) genre, the nutshell of it is you must prevent swarms of enemies from traversing a path across the playfield by deploying active and passive defensive structures (colloquially just ‘towers’) along the route.  S2 then is a fixed-path TD which means you have no control over the route enemies take; just need to stop ‘em from taking it.  All towers from S1 are back with the addition of 1 new one, the booster which has no direct attack but grants  a damage and range bonus to all towers immediately adjacent to it (8 max).  All towers can be upgraded thrice and have a unique graphic representation at each point.  Notable is the final upgrade for each tower which has been beefed up to make it much more worthwhile to save up the extra cash to achieve.  The 2 things S1 brought to the table that I felt unique and very cool were the drones and barriers; thankfully both have been further fleshed out for S2.  The standard repair/resource collection drone can now be given a priority to either always collect resources (money) regardless or repair first and then collect.  New is the energy drone which will boost energy production.  Energy collection is a new concept and used to power 4 orbital attacks from Sentinel: homing missiles, attack drones, time warp (slows enemies) and the almighty orbital laser for those times when only total annihilation will do.  You collect energy to power these attacks slowly over time but can boost it with drones and barriers.  There are 4 barrier types in S2 now: standard which just blocks enemies, pipeline which grants cash after each round, energy which grants energy after each round and double which blocks 2 paths at once.  A big key to success in S2 is building up energy production so your orbital attacks are on tap as often as possible.  All alien types are also back from S1 with the addition of 1 new boss, the Arthropod Parasite.  The graphics in S2 are as stunning as the original with gobs of animation and detail.  An all-new soundtrack from Specimen A rounds out the intense audio-visual feast of S2.  Origin8 have finely honed their craft here as the game is capable of rendering a massive amount of action in uber-high detail with nary a framerate hit in sight.  That said, if I could nitpick on 1 thing, I’d like to see a little more ambient detail such as waves breaking, palm trees swaying and such as the backdrops are a bit on the (lovely but) static side.

S2 features 2 modes of play: campaign and mission.  Campaign mode consists of completing a set number of waves on each of 4 progressively unlocked maps at your choice of 3 difficulty levels.  Once you beat a level you unlock endurance or ‘freeplay’ mode where you can just play forever or until the aliens stomp you.  New for S2 is mission mode which is a series of 10 progressively unlocked challenge levels (using the same maps) that give you specific victory criteria such as a set amount of money to work with or access only to orbital weapons.  Mission mode is quite a lot of fun and a welcome addition; would in fact like to see more such levels!  Finally, the game features superb global leaderboard support using Openfeint which just plain works really well in addition to enhancing replay value.

Alright, onward with the gripes and suggestions.

  • No ingame music or sound volume control; would really like to see this added.
  • No screen flip.  Not sure why this feature is so often overlooked, everyone wants it but it continues to be elusive.
  • No manual targeting for towers (like Sweetwater Defense).  Granted this is something of an up and coming feature in TD games but it would be nice to see it adopted here.
  • The build menu at the bottom of the screen can become obtrusive so would really like to see it auto-hide after a few seconds or something.  Not only would this show more of the screen and enhance the visual enjoyment but more importantly prevent accidental tower deployment.  Far too many times while just zooming/scrolling during the normal course of gameplay my finger caught a tower and ended up building it at some random location unintentionally.
  • It’s too easy to mistakenly sell a tower.  When you want to deselect a tower you have to touch an unrelated part of the screen but on several occasions in the stress of battle I accidentally hit the sell button which is incredibly frustrating.
  • Not as common but still frustrating is the possibility of upgrading the wrong tower when there’s a big cluster of them together.  In what is possibly the only downside to the detailed graphics, visual clutter can definitely become an issue on the small display.  I think a simple ‘undo last move’ feature would go a long way towards addressing these last 3 points.
  • Oddly, the game became at times completely unresponsive to touches, something I also noticed in S1.  Not sure what would cause this but again highly frustrating in the heat of battle.
  • Game seems a bit of a battery hog so just be aware during long play sessions.
  • A gripe shared also with S1 is that there’s no story to unfold; you get a blurb at the beginning about your base under attack and from there it’s just play the maps.  A minor gripe for sure but Sentinel in particular just seems ripe to at least try and tell us a cool SciFi story to go with the awesome production values.

People who have never played Sentinel 1 should just buy Sentinel 2: Earth Defense right away and commence to playing this awesome game.  Some debate exists among S1 veterans though as to whether S2 should really have been released as a sequel or simply as an (lower-priced) update to S1.  After playing both games extensively, there’s no question S2 feels like S1 about 85% of the time and there’s certainly something keen about having your entire Sentinel fix in just 1 app.  That said, it’s a fine line indeed and not the point of the review but I think specifically the orbital weapons and energy collecting, extra value attached to protecting barriers, definitely mission mode and to a lesser extent the booster tower make for enough new strategic elements and fun to call it a worthwhile purchase for S1 fans.  Personally I’m tending to think of it as ’standalone DLC’ for the original and $3 really isn’t too much (plus OS3 gives us 2 more pages in the Springboard so what the hey).  I will say that I’m definitely looking forward to what Origin8 can come up with next given their obvious talent  (which is a subtle way of saying I hope Sentinel 3 is not in the pipeline).  Bottom line then is Sentinel 2: Earth Defense is a very high-quality TD game that does not disappoint and has enough new elements to keep veteran S1 players entertained.

version reviewed – 1.1
reviewed on – iPhone 3GS 16GB OS3.0
screen flip – sadly, no
iTunes music support – yes (OS3 required)









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