## 4 Discussion
### Merits of the Proposed Role-Play System for Puppetry  
Some merits of the proposed role-play system are described in the following.  
1. _The proposed system was designed from a user-centered viewpoint --_  
According to the user-centered design (UCD) theory, the product should conform to the user's needs rather than let the user adjust the product [48]. The design of the interface with the user must also be consistent with the user's habitual way of product operations. In the role-play process of the proposed system, the user can understand the characteristics of various roles by operating the puppets, uttering the narrations, and learning the puppet figures. When a user picks up the puppet and goes to the simulated stage as a puppet performer, a background image matching the puppet character is projected on the background screen, and matching music is played synchronously (see Figure 9). All these arrangements were designed in this study to meet the needs of the user's puppet performance.  
2. _The proposed system provides a simple and intuitive operation process for the user --_  
According to past experiences of watching the puppetry, the user does not have to spend a lot of time locating, assessing, and reading the introduction [49]. The role-play operations carried out on the proposed system were designed with the most intuitive and humanized interfaces, which allow users to participate in the operations only according to their common cognitive habits. Without too much explanation and learning operation instructions, all the processes can be completed easily. Furthermore, in order to facilitate users to operate puppets, the stage is lowered, especially so that users can see the situation of their own operations of the puppets. Either a single person or two persons can operate the puppets on the stage in sequence or together (see Figure 11). They do not have to care whether they are as professional as puppeteers; as long as they are willing to get involved in the experiencing environment, they can obtain unforgettable experiences.  
3. _The proposed system provides an easy and realistic operation environment for the user --_  
In order to facilitate users to experience the role-play themselves, the props used for displays in the puppetry, including the stage, lighting, and AV speakers and screen that are recognized by ordinary people, have all been created in this study; the user can only pick up a puppet of the desired role, and put it on the palm to carry out the puppet performance. Not only do the tangible equipment itself and the puppets have the same appearance designs as those in the actual puppet show, but the operation process does not need complicated explanations and detailed instructions, which conform to the basic principle  
Figure 11: Two performers operating puppets on the simulated stage of the proposed system.  
of _easiness_ in the design of 3E interfaces. After all, puppetry has a considerable degree of connection with the lives of all ethnic groups in the world, and it is desired that the role-play-based learning of puppetry could be designed to be as close to real puppet shows seen by the public as possible.
4. _The construction of the proposed system is cost-effective, considering the above-mentioned merits --_  
According to our experiences of developing the proposed system and helping a well-known theater company to create a similar system, it needs about USD 4000 to construct each system. The total expense is not high because the used electronic media equipment is simple, the program structure is not complicated, and the most important thing is that the system's stability is high with a low maintenance cost. Furthermore, the number of puppet roles can be easily increased, additional puppet show contents can be added, and the time to construct the proposed system needs no more than two months, meaning that the proposed system is cost-effective.