Methods by which companies are trying to make virtual keyboards feel like real ones

Five methods come to mind, which can be grouped by three fundamental human senses:

1. Visual/Color: Change the color of the key which is pressed/touched (momentarily).
2. Visual/Size: Increase the size of the key (again, momentarily).
3. Visual/Animation: Animate the movement from the original size to the larger size.
4. Audio/Sound: Make a clicking sound for each keystroke.
5. Touch/Vibration: Vibrate the device to indicate that the key has been pressed.