Research and discuss existing approaches to alphabetical and numerical input in head-mounted display virtual reality. Based on the outcomes of the research and identified challenges, implement a virtual reality application, built on top of the Unity game engine, containing the following features:

• Five different methods of numerical (0-9) input
• Five different methods of alphabetical (A-Z) input
• A simple user interface that will allow the user to test any of the input methods above

The application should be designed for the HTC Vive device and its controllers. Describe all of the implemented methods, emphasizing their advantages and drawbacks as well as possible use cases. Besides that, compare the proposed methods focusing mainly on:

• speed of typing
• error rate
• efficiency (size) of the keyboard layout

The results of the comparison should be summarized and discussed, taking existing methods and their results into consideration.