**3.4 TWTD design**

Figure 3 depicts the main layers of TWTD. In TWTD version 2, the databases were hosted on the cloud using Microsoft Azure cloud to accommodate larger databases and more subjects.

### **How touchless SDK was modified?**

We modified touchless SDK to comply with hand disabilities. The original library has 3 markers. We customized the library to use two markers instead [9].

Towards Economical E-Learning Educational Environments for Physically Challenged Students 23

Figure 5 depicts a snapshot of a handicapped student starting to use TWTD version 2. The markers are attached to the remains of the user's arms. In the figure the user is about to choose a given lesson out of the different options: English, Math, Shapes, Science). The

applications are mainly what public schools offer in Kuwait.

Fig. 4. Class Diagram of TWTD.

**3.6 Using TWTD 2** 

Fig. 5. Setting up markers.

Fig. 2. Use Case Diagram for TWTD.

Fig. 3. Architecture Diagram of TWTD.

Figure 4 depicts the main classes of TWTD. The main classes are following PLITS [3] (a pattern language for constructing intelligent tutoring system). The details of using PLITS in developing TWTD are discussed in details in [9].

Fig. 4. Class Diagram of TWTD.
