# Extended Reality (XR) Engines for Developing Gamified Apps and Serious Games: A Scoping Review
## 4 Discussion
### RQ3. What Serious Game Attributes Are Supported in XR Game Engines?
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Extended** & & & & & \\
**Reality Engine** & **Rules** & **Goals and Choices** & **Task/Challenges** & **Collaboration and Competition** & **Feedback/ Assessment** \\ \hline Google & RL1, RL3 & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC10, CC3, CC4, & FA1, FA2, FA5, \\ ARCore & RL6, RL2, RL5 & GC4, GC5, GC6, GC7 & TC5, TC7 & CC6, CC7, CC8 & FA6, FA8 \\ \hline Apple ARKit & RL1, RL2, RL3, & GC3, GC4, GC7 & TC1, TC2, TC7 & CC10, CC3, CC4, & FA1, FA2, FA6, FA8 \\  & RL5, RL6 & & GC3, GC4, GC7 & TC1, TC2, TC7 & CC10, CC3, CC4, & FA1, FA2, FA6, FA8 \\ \hline Unity 3D & RL1, RL2, RL3, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC1, CC10, CC3, & FA1, FA2, FA3, \\  & RL5, RL6 & GC4, GC5, GC6, GC7 & TC5, TC6, TC7, & CC4, CC5, CC6, & FA4, FA5, FA6, \\  & & TC8, TC9 & CC7, CC8, CC9 & FA7, FA8 \\ \hline Vuforia & RL1, RL3, RL5, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC1, CC10, CC3, & FA1, FA2, FA3, \\  & RL6 & GC4, GC5, GC6, GC7 & TC5, TC6, TC7 & CC4, CC5, CC6, & FA4, FA5, FA6, FA8 \\  & & CC7, CC8, CC9 & & CC7, CC8, CC9 & FA3, FA4, FA5, \\ \hline Unreal Engine & RL1, RL2, RL3, & GC1, GC2, GC3, & TC2, TC3, TC4, TC5, & CC2, CC4, CC5, & FA2, FA3, FA4, \\
5 & RL5, RL6 & GC4, GC6, GC7 & TC6, TC7, TC8, TC9 & CC6, CC7, & FA5, FA8 \\  & & CC8, CC9 & & CC8, CC9 & \\ \hline Nuke & RL1, RL2, RL3, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC1, CC10, CC4, & FA3, FA4, FA5, \\  & RL5, RL6 & GC6, GC7 & TC5, TC6, TC7, & CC5, CC8, CC9, & FA6, FA8 \\  & & TC8, TC9 & CC6, CC7, & FA4, FA5, FA6, FA8 \\ \hline HeroMirror & RL1, RL2, RL3, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC4, CC5, CC6, & FA1, FA2, FA3, \\  & RL5, RL6 & GC4, GC5, GC6, GC7 & TC5, TC6, TC7, & CC7, CC8 & FA4, FA5, FA6, FA8 \\  & & TC8, TC9 & & CC9, & FA1, FA2, FA3, \\ \hline Godot & RL1, RL2, RL3, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC10, CC3, CC4, & FA1, FA2, FA3, \\  & RL5, RL6 & GC6, GC7 & TC5, TC6, TC7, & CC5, CC6, & FA1, FA2, FA3, \\  & & TC8, TC9 & & CC8, CC9 & FA4, FA5, FA6, FA8 \\ \hline Verge3D & RL1, RL2, RL3, & GC2, GC3, & TC2, TC6, TC8, TC9 & CC10, CC5, CC6, & FA1, FA2, FA3, \\  & RL5, RL6 & GC1, GC2, GC3, & TC5, TC6, TC7, & CC2, CC3, CC4, & FA4, FA5, FA6, \\  & & TC8, TC9, TC9, & CC8, CC9, & FA7, FA8 \\ \hline Amazon & RL1, RL2, RL3, & GC1, GC2, GC3, & TC1, TC2, TC3, TC4, & CC1, CC10, CC11, & FA1, FA2, FA3, \\ Sumerian & RL5, RL6 & GC4, GC5, GC6, GC7 & TC5, TC6, TC7, & CC5, CC6, & FA4, FA5, FA6, \\  & & TC8, TC9 & & CC8, CC9, & FA7, FA8 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Serious game attributes supported by proprietary XR game engines. In the Tasks/challenges category, the objective stems from learning that originates from task completion. During a serious game, the player needs to separate task-relevant from task-redundant information and determine the inherent complexity of game tasks. An overarching task of the player is to become familiar with the rules, controls, and logic of each level for adjusting gameplay. The game attributes for this category are NPC-based task descriptions, progress bars, multiple choice, major tasks, branch tasks, puzzles, research points, study, and requirements. The proprietary XR game engines with weaker game attribute support are Apple ARKit and Verge3D. In this category, the XR game engines Unity, Nuke, HeroMirror, Godot, and Amazon Sumerian support all game attributes. The game attribute progress bars are the only game attribute supported in all of the proprietary XR game engines. In the JavaScript-based XR engines, all game attributes are supported except branch tasks, which are unsupported by A-Frame, React XR, and the Wonderland Engine. The Collaboration and Competition category establishes that collaboration is a key factor in multiplayer gameplay, and while competition is at the core of most online games, working with other players is often just as compelling as working against them.