iPhone 4: The developers speak out on retina displays and gyroscopes

The iPhone 4, revealed earlier this week at Apple's annual development pow-wow WWDC, is packed to the gills with sensors, cameras, and new technology. A sharper screen, a brand new design and even a gyroscope, just for kicks.

Apple is marketing it as the biggest jump forward since the original iPhone hit the scene in 2007.

For gamers, its advances are a little more subtle than greatly improved snappers and Back to the Future style video calls.

But it's still got some rather weighty implications for the gaming world, so we asked three top iPhone developers to give their snap reactions to Steve Jobs's keynote.

The iPhone 4 packs a remarkably upgraded screen from the 3GS. Not only does it feature a whopping 326 DPI display, but the resolution has been upped four times to an enormous 960x640, just a few pixels off the iPad's screen resolution.

Hitting close to the iPad's resolution makes a handy starting point, says Jani Kahrama from Zen Bound developer Secret Exit.

"At a glance it seems the new screen would be good for using iPad assets in an iPhone layout," says Kahrama.

Michael Schade from FishLabs, the developer behind Galaxy on Fire, agrees, saying "with the iPhone 4 we have just another device to justify the extra development effort" of supporting the iPad.

Schade also makes the interesting point that with the high resolution assets for the iPhone 4 and iPad, developers are in a great position to do versions for PC and services like Xbox Live Arcade. "With iPhone 4, the three screen media environment becomes reality," he says.

Kahrama says, "if there are still developers who aren't developing their source assets in high resolution, now would be the time to start thinking about scalability."

But higher resolution assets mean a larger budget, says Luke Ryan from Jet Car Stunts developer True Axis. "Higher quality art is needed which will increase costs," he says, "although, you can still get away with more on such a small screen."

Saturating your own market with loads of different devices quickly confuses things. Just ask our mobile editor Jon Mundy. With iPhone, iPad and now iPhone 4, there are more screens than ever to make games for .

"Capability fragmentation is a little scary, and there is a temptation to always design for the lowest common denominator to cut costs," says True Axis's Ryan.

When you've got nearly 100 million devices out there that are running the age old 320x480 resolution, is it worth the effort and budget to super size the games?

"The number of devices we have to test for is also now getting big, you really need to test on every device to be safe," Ryan explains. The average iPhone developer needs a fleet of Apple gear just to make sure the game runs as designed.

All three of the developers we spoke to have made games that use the iPhone's accelerometer, letting you steer cars, space ships and blocks of wood shaped like joysticks just by tilting your iPhone.

They know Apple's motion-sensing tech like no other, so what do they think of the new gyroscope?

Giving games a few extra axes of movement quickly got our developers thinking. One idea: the player could, "turn the phone like a steering wheel to turn, or like bike handles to look around corners," says Ryan, "for Jet Car Stunts, it could be used to make a huge difference to the in-air controls."

Fishlabs's Michael Schade points out that in a racing game using the gyroscope you could, "take down your opponent with a hefty bump to the side while you keep the line with the accelerometer."

And on the subject of space games (Galaxy on Fire 2 for instance), he rhetorically asks, "how cool would it be docking carefully to a space station or landing on an asteroid using the gyro to control speed and angle in all three dimensions?"

Very cool, is the answer.

Secret Exit's Jani Kahrama wants to get his mitts on the new iPhone before deciding, but says that "subtle controls that complement the gameplay" are the key to a good motion tracker, rather than large arm waving movement, and that the "new capabilities are interesting".

Giving some iPhones a fancy gyroscope while old devices lose out provides yet more tricky parity and legacy issues for these developers.

"My biggest concern is that it would give people an unfair advantage on the leaderboards when competing against players with non-gyro hardware," says Ryan.

"We have to keep in mind that there are a lot of devices without gyro so we can't change the whole gameplay," says Schade, with regard to adding gyro support to Galaxy on Fire 2. "The more innovation Apple brings to the table the more fragmented the market gets."

So it seems that these developers are all excited, yet have ample trepidations, about the new tech being packed in Apple's next phone.

All three are interested in supporting the new device in some way. "We can't wait to see Zen Bound 2 running in native resolution on the Retina display," says Kahrama, "We would love to have gyro support in Galaxy on Fire 2," says Schade.

Luke Ryan has no plans yet, but True Axis is "starting to move our focus to the sequel (to Jet Car Stunts) and making that as good as possible," so we should see some iPhone 4 enhancements there.

iPhone 4 will be released on June 24th.