A couple of weeks ago we took an exclusive hands-on look at the puzzle platformer GravBot [Free] from Team Phobic, the developer responsible for games like Bounce On [$1.99/Lite], Bounce On 2: Drallo's Demise [$3.99/Lite], and Tunnel Shoot [99�]. Earlier tonight, the game went live in the US App Store. GravBot is free to download and initially comes with 12 levels. These levels ease you into the game mechanics and give you a great taste of what GravBot has to offer. If you like what's contained in this glorified demo, then there are two additional level packs available as in-app purchase. Each of these level packs contains 20 increasingly difficult levels, and are 99� apiece. Here is an excerpt from our hands-on preview talking about the gameplay in GravBot:

In�GravBot, you'll play as a tiny robot who must collect all of the batteries on each perilous level. In order to accomplish this, you can spin the entire level either 90 degrees left or right or entirely upside down to change the direction of gravity. Your robot can travel left and right on its single tire, and will fall towards whichever way happens to be down at the time. Levels are filled with hazards like spikes, enemies, and lasers which will kill instantly if not avoided. The batteries can be tricky to get to, and a color-coded system of trapdoors, elevators, and various other obstacles will need to be triggered by switching a lever or pushing blocks onto buttons � all in the name of snagging every last battery on a given level.

While just completing each level is sufficiently challenging and fun, the real hook toGravBot is trying to obtain gold medals for each one. The game keeps track of how many times you switched gravity to complete a level, with bronze/silver/gold medals awarded for using it efficiently. What is really satisfying is when you figure out a way to win gold using fewer gravity switches than is required. Due to the physics engine in the game, you can sometimes make it to a hard to reach area without changing the gravity and instead gliding through the air or just barely catching the edge of a platform and hanging on.

There's really not anything I don't like about GravBot, and it has become one of my most favorite puzzle games that I've played on the iPhone. The graphical style is cute, with support for Retina Display, and the GravBot robot exudes a ton of personality in the game. The levels are all really cleverly designed, and there's a tremendous amount of replay value going back to each one and trying to complete it in the most efficient way possible, earning medals and competing on the Plus+ leaderboards as you go. There's no risk in downloading the game for free and trying out the initial 12 levels, and the IAP level packs offer a great value for money if you're looking for more. In fact, I would love to see some additional level packs released down the line sometime. Players in our forums are enjoying the game�as well, and it appears that the talented folks at Team Phobic have another hit on their hands with GravBot.

We're not sure what has possessed the publishers of dozens of amazing iPhone games to decide that tonight was the night to hold a massive sale � but it's happened. And you can benefit from it.

A huge number of high profile games have dropped in price to all time lows. The number of high quality games you can pick up for $0.99 right now is amazing. We hand picked a few to highlight here, but below we've listed dozens more. Every game on this list is worth the sale price, so now's your chance.

A few notable games dropping to $0.99 include:

Osmos, $0.99 Osmos was originally released in late August of 2009 for the PC, and went on to win numerous awards. The multi-touch controls work wonderfully on the platform and it's a natural fit for the iPhone. We highly recommend picking this one up. Review

Spider: The Secret of Bryce Manor, $0.99 We choose Tiger Style Games' Spider: The Secret of Bryce Manor for our 2009 Game of the Year. Spider is an original concept built specifically for the iPhone by a small self funded team. Review

2K Sports NHL 2K11, $0.99 It wouldn't be hard for NHL 2K11 to claim the title of best ice hockey game on the iPhone, since the competition is sorely lacking. But it surprisingly goes above and beyond and offers a truly full-fledged NHL experience on a mobile platform. Review

Archetype, $0.99 Archetype delivers one of the most robust, beautiful, and most importantly fun first person shooter (FPS) experiences that can be had on the iPhone. Review

Here's the rest of the list, grouped by price. Unfortunately, this appears to be an iPhone / iPod Touch phenomenon mostly. Only two games (marked below) are iPad native.

$0.99

• Civilization Revolution ($6.99 -> $0.99)
• Soccer Superstars ($2.99 -> $0.99)
• 9 Innings: Pro Baseball 2011 ($4.99 -> $0.99)
• Baseball Superstars 2010 ($2.99 -> $0.99)
• Need for Speed Shift ($6.99 -> $0.99)
• Bookworm ($2.99 -> $0.99)
• Geometry Wars: Touch ($4.99 -> $0.99) Universal
• Puzzle Agent ($4.99 -> $0.99)
• Monkey Island 2 Special Edition ($2.99 -> $0.99)
• The Secret of Monkey Island Special Edition ($2.99 -> $0.99)
• Doom II RPG ($3.99 -> $0.99)
• Assassin's Creed II ($5.99 -> $0.99)
• Zombie Infection ($2.99 -> $0.99)
• Peggle ($2.99 -> $0.99)

$1.99

• Crash Bandicoot Nitro Kart 2 ($4.99 -> $1.99)
• Risk: The official Game ($4.99 -> $1.99)
• Hybrid 2: Saga of Nostalgia ($4.99 -> $1.99)
• Zenonia 2 ($4.99 -> $1.99)
• Castlevania Puzzle: Encore of the Night ($4.99 -> $1.99)
• Mirror's Edge ($4.99 -> $1.99)
• ACE Combat Xi: Skies of Incursion ($4.99 -> $1.99)
• Myst ($4.99 -> $1.99)
• Doom Resurrection ($6.99 -> $1.99)
• Sonic the Hedgehog 2 ($5.99 -> $1.99)
• Tony Hawk's Pro Skater 2 ($4.99 -> $1.99)
• NCAA Football by EA Sports ($4.99 -> $1.99)
• Command & Conquer Red Alert ($4.99 -> $1.99)

$2.99+

• NFL 2011 ($4.99 -> $2.99)
• Real Racing ($4.99 -> $2.99)
• Call of Duty Zombies ($9.99 -> $4.99)
• Call of Duty Zomies HD ($9.99 -> $4.99) iPad Only
• FIFA 10 by EA Sports ($6.99 -> $4.99)

The newest game from developer John Kooistra and Cat in a Box Games, Blue Defense: Second Wave! [99�], has just been released to the US App Store. Blue Defense: Second Wave! is the sequel to the 2008 game Blue Defense! [$1.99] that was one of the earliest success stories in the fledgling days of the App Store. Blue Defense! became popular by offering a challenging game with simple mechanics, clean graphics, and smart use of the unique strengths of the platform. Blue Defense: Second Wave! retains these core beliefs, and expands on them in a number of ways to provide a game that feels both fresh and familiar. Here is an excerpt from�our hands-on preview that explains some of the gameplay found in Blue Defense: Second Wave!:

The basics of Second Wave remain the same. You'll fight off waves of enemies with a perpetually shooting cannon firing from the center of the planet which you're trying to protect. A population of about 7 billion people act as the life of your planet, with that number dwindling with every enemy that penetrates your defense. If the population hits zero, the planet is lost and it's game over.

One of the biggest changes this time around is the ability to fire multiple cannons at once. Touching the screen at any time brings up an aiming reticule and a new stream of fire, with multitouch support for adding up to five additional streams along with the first cannon. A quick double tap on the screen locks an aiming reticule in place at that point on the screen, which can be dragged around and set anywhere you want to direct more firepower.

…

Besides the ability to add streams of fire, you also get a new weapon in the form of the planet cannon. Touching your planet and swiping in the direction you want to fire launches a humongous beam of destruction that's as wide as the planet itself. The planet cannon vaporizes anything in it's path, but comes with limited uses.

If you were a fan of the first Blue Defense! then you will most certainly enjoy this new sequel. If you somehow missed out on the first game, then Blue Defense: Second Wave! offers a stimulating shooter experience with unique mechanics that have evolved and been refined in the nearly two years since the first release. Best of all, Blue Defense: Second Wave! is launching at a special introductory price of just 99� through this weekend. It's also a universal app that will run on all iOS devices and has graphics that support the Retina Display. With 64 levels to play, more than 200 medals to earn, multiple modes of play, online leaderboards, and more, there is a ton of content for the price and Blue Defense: Second Wave! is a game that's not to be missed.

Just two days after we took a hands-on look at ARDefender from developer Int13, the game has now become available in the App Store as of this morning. What is a nice surprise is that the game has launched for just 99�. In ARDefender, you'll print out a special PDF image from ARDefender.com that is read by the software and creates a 3D tower in the real-life space of the iOS device camera's view. Enemies then attack the tower from all angles, and you fend them off with a weapon placed on top of the tower. You'll have a machine gun, rockets, and a laser at your disposal as you take on the endless waves of increasingly difficult enemies.

It's a cool concept and one that works really well in practice. I was blown away with how convincingly the tower seems to actually exist in the area where you're playing the game. The gameplay itself is also quite fun, although pretty bare bones. There's really only one mode to play through in ARDefender which has you defending against seemingly endless waves of enemies. Beyond that, there's not a whole lot more to the game. I'd love to see something along the lines of a story mode, different styles of towers, or online leaderboards and achievements. Still, what's here in terms of gameplay is pretty darn fun anyway. This video shows off one round of ARDefender as well as me playing around a little with how the technology works:

One thing that is important to take note of is that ARDefender will not work with the original iPhone or iPhone 3G. It would make sense that the older iPod touches would not run the game as they don't have an external camera (the game does run on the new camera-enabled 4th generation iPod touches by the way), but apparently ARDefender requires some processing power that needs at least a 3Gs iPhone or above.

Normally when a game only has one mode to play with not a lot of bells and whistles, it can be hard to recommend as those games tend to get old pretty quickly. In ARDefender's case however, the technology is just so impressive and the gameplay is so well done that it's hard to pass on the game when it's only a dollar. It's definitely something you'll want to show off to your friends because it's so neat, and players in our forums are already finding all of the wacky places they can place the PDF image and play the game (including pulling up the image on a second Apple device and growing the tower right out of that device's screen). If you have a dollar to spare and a capable device, you should definitely give ARDefender a try.