If you are a fan of tower defense games, here is one to add to your collection. Sentinel, by Origin8 Technology, takes the genre to another world -- literally.

In the year 2029, humans have begun to colonize Mars and establish mining operations. Soon alien forces begin to attack and you’re beckoned to help. You play as the commander of the Sentinel, a dropship sent to Mars. Organize and build your defense quickly to ward off waves of oncoming enemy troops. At your disposal are weapons in the following categories: Lasers, Bombs, Beam, and Sniper. Weapons have varying degrees of influence but all can be upgraded, granted you have the cash. That’s right; all weapons require funding to purchase. Acquire funds for every alien troop defeated. Cash can also purchase repair drones -- a must have once you begin to retain damage.

Origin8 has supplied a sufficient amount of alien types. Arachnids are insect-like troops that move fast but are pretty weak. Mutants are more durable robotic soldiers that move at mediocre speed. In the same speed and strength class are Winged Parasites. These can only be defeated with surface-to-air weaponry. Another enemy is only defined as Slow Walkers. These huge beings move at a snail’s pace but require tons of force to bring them down. If enemies succeed in defeating your structures, they will reach your base and then its game over for you. On the upside, you have up to 120 waves to overcome them.

The team at Origin8 continues to wow AppSmile by their inclusion of online options. Recently they updated Sentinel to include a friend challenge that lets you email a buddy from your Contacts and taunt them to beat your score. Scores can also be submitted to an online community.

It’s obvious to the AppSmile Team that the guys at Origin8 have it goin’ on. They have delivered an exciting tower defense game in all respects. Hats off to Sentinel.

Here’s our AppSmile List of Favorite Features:

• A fantastic user interface presenting well designed, high quality menus and instructions
• Increasing difficulty levels throughout each board
• No two game play periods are alike
• Proper use of the iPhone’s touch screen; drag and drop weapons, pinch to zoom, slide to scroll
• Pause and Fast Forward buttons
• Superb graphics including aliens and environment
• Each enemy soldier displays its individual health level

AppSmile Team’s Wish List:

• Once weapons are in place we would love to be able to switch to a 3D viewing angle
• Additional levels with more enemy types

Sentinel gets our AppSmile 5-Dimple rating: