The user interface of iOS consists of a 4x4 grid for iPhone and iPod touch, and 4x5 for the iPad, and will always have a dock at the bottom of the screen. Some interaction is performed using touch gestures, such as tapping, swiping, pinching, and sliding, other forms of interaction will require using the gyroscope, accelerometer, using the camera, or speaking into the microphone. Internal accelerometers are used by some applications to respond to shaking the device (for gaming, this would be used to tilt a sprite in a direction, such as in Doodle Jump).
Apple had released the iPod touch, which had most of the non-phone capabilities of the iPhone. Apple also sold more than one million iPhones during the 2007 holiday season. On January 27, 2010, Apple announced the iPad, featuring a larger screen than the iPhone and iPod touch, and designed for web browsing, media consumption, and reading iBooks, and most apps from the iPhone would become re-released either universally or in HD. Most "classic" titles were released in the 2009-2010 era.