9 Unique Apps to Try on the iPhone Duo

Key points

• Apple's iPhone Duo has prompted developers to build quirky apps that use its folding design. Battlefleet Duo lets players sit across from each other in tabletop mode for local multiplayer games.
• Flipcorder turns the phone into a retro camcorder, with a preview on the outer display. RectoVerso uses the hinge as a flashcard reveal, and PianoFold is a rhythm game played at a 90-degree angle.
• Other picks include Toastie, a sandwich-making game, and Portal, a relaxing soundscape app.