A while back, I reviewed these games.  Unfortunately though, the posts have somehow disappeared.  The recent move of the blog and changing of the perma-links might have something to do with it.  Regardless of why they are gone though, it is a perfect excuse to revisit these incredible titles and highlight some of the changes and updates in them.

Sentinel, at it’s core, is one of the best Tower Defense games out there.  Set in a sci-fi “Mars Defense” theme, the graphics will blow you away.  Prior to playing Sentinel, I thought that Fieldrunners was probably the best TD game for the iPhone.  As soon as I launched Sentinel though, I was immediately re-thinking that idea.  This impression was not just because of the quality of the graphics, but of how the graphics actually work into the game play to give it almost a 3-D effect.  For example, your enemies may have to run a gauntlet between buildings and you can place your towers on those buildings to fire “down” into the path that the enemy is forced to use.  From a programmer standpoint, I realize that this is not much more than any other forced TD enemy path, but the implementation makes it seem much more than that because the landscape plays a more visual part of your strategy.  Instead of a typical enemy path being seen as a limitation to them, it flips that idea so that terrain comes across as something you can use to your advantage.    This terrain feature is enhanced with the addition of temporary barriers that the enemy can eventually tear down and get through.

Sentinel  allows you to defend your base in typical TD fashion with five tower types against four enemy types with three different terrain maps and two different modes of play, but comes with a bit of a real-time strategy feel to it as well because you can also harvest resources and create robot droids to repair your towers.  These additional features make this $0.99 game (originally priced at $4.99 and worth it) a real competitor to the $2.99 Fieldrunners.  And, if you watch for it on AppShopper.com, the developers even drop the price to free on occasion!

Sentinel 2 brings the same look and feel and great graphics down to earth in a “Earth Defense” theme.  But the Origin8 developers didn’t just create the same game with different graphics.  This $2.99 sequel improves on Sentinel with additional OpenFeint features (location based leader boards), further RTS-like features of attack drones and additional harvest drones, and special weapons that can be fired from space once enough energy is harvested from the playing field.  There is also a new booster tower that can be strategically placed to “boost” the effects of your other towers.  And, in addition to upgrading your placed towers, you can also upgrade your ship from which the towers and such are deployed.

The timeline of the game really ties into the first title.  In this game, your “Mars Defense” has failed and the enemy has set it’s sights on Earth.  The game offers four different “locations” on earth that serve as different playing maps, and four different levels of difficulty.  This will, guaranteed, provide any experienced TD player with enough to challenge the very best of their efforts.  Both endurance mode and mission mode (with 10 pre-defined missions) are available as well.  And, because this title builds on both the original Sentinel story line and technology, I’d recommend starting with Sentinel until you get the basics down and then progress to the further depth that Sentinel 2 has to offer.

If you enjoy quality games of this type, you also need to check out the new release, Space Station: Frontier, by the same developers.  All three truly take the Tower Defense genre to whole new levels and, along with Chillingo’s Defender Chronicles, probably offer the best this genre has to offer on the iPhone platform.  Needless to say, both of these titles make it to my Must-Have category.