There are times when companies make things because they can, rather than because there is a need to. So why has the LG GD900 Crystal handset got a slide-out transparent keypad? We had a play at the UK launch to try and answer that question ourselves.

First announced at Mobile World Congress in Barcelona, the much talked about mobile phone is finally due to hit the shops in the UK in July. Since its initial outing we've seen it at CITA in the USA and then finally at the end of May at the UK launch. The model we played with is virtually the final thing with the usual last minute software tweaks still needed before it ships.

Whip the phone out of your pocket and the chunky slider handset offers a 3-inch LCD touchscreen display with haptic feedback and a see-through keypad. Yes the keypad is see-through, supposedly so you can see what you are doing behind the phone.

Why? We aren't really sure why and you get the feeling that the Koreans who came up with the idea don't know either. That's not to say it doesn't work or it's no good, but we still can't really get our heads around the why???

Getting past the "WHY?!?" for a few seconds, and you realise that the technology behind it is actually very clever. The keypad isn't just a piece of plastic with some numbers drawn on it, it is actually a touchscreen display which just shows numbers.

What this actually means is that you can, and you will, use the keypad to control certain elements on the screen without actually touching the main screen.

The confusing part for some is that the main screen is a fully enabled touchscreen as well with Multi Finger Touch support like the iPhone. Just as you would expect, you can use the pinch zoom functionality when web surfing, photo viewing, or watching a movie.

Still those who don't want to clutter their screen with their fat fingers can use the keypad very much like they do a trackpad on a laptop. Jump into the camera mode for example and you'll be able to spin your finger around in a circle on the keypad to zoom into the shot you want to take.

On the browser you get to use the keypad just like you would a trackpad, with your finger controlling the mouse pointer. And yes tapping it selects the link. You'll also be able to use the transparent keypad for "finger-writing recognition" for writing emails and to set-up shortcuts, so drawing the letter "M" launches the music player for example.

Beyond the transparent keypad the GD900, or Crystal as it is also known, offers the company's new S-Class operating system as found in the Arena. Very iPhoney in its look and feel, but 3D. It's easy to use with plenty of options to allow you to get the most out of the handset's features.

Those features include HSDPA and Wi-Fi connectivity, an 8-megapixel camera, which is revealed when the slider is opened and the usual array of Bluetooth, accelerometer for automatic landscape mode and music and video players. There is a microSD slot, which is revealed when you slide open the handset, and it will support cards up to 32GB in size.