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NTT DoCoMo and Fujitsu developed a new smartphone with transparent display and multi touch on both sides.
By using it from the back, you can scroll the screen without obscuring the display, and reach the slide down notification bar easily with your index finger.
Docomo also implemented a new way of using smartphones, by touching both sides at once.
You could hold down an icon on the front, and slide on the back to move an icon, or use the message bar, or create a new application. Read more for video presentation and more details.
For example, from the front, you can only move the whole Rubik cube like this, but if you slide your finger across the front while holding down the back, you can rotate just one face. So this display makes gripping operations possible. Compared with a standard smartphone, this one still has slightly low brightness, so it's a bit hard to view in bright places, but I thing this thing is going in the right direction.