Toward a Theory-Driven Model of Emotional Interaction Design in Mobile Games Research -- A Specific Measurable Model - How Can Test Results be Influenced by Interactive Prototypes and Design Manuscripts? -- HEROES: an Action Game enabling Players With and Without Disabilities to Play Together -- Gaze as a Navigation and Control Mechanism in Third-Person Shooter Video Games -- Foresthlon: Investigating Gender Experience through a Hybrid BCI Game -- Research on User Experience Optimization for Tutorial Design of Battle Royale Games Based on Grey AHP Theory -- Horror Ludens: Using Fear to Construct Meaning in Video Games -- Persuasive Technology in Games: A Brief Review and Reappraisa -- Analyzing and Prioritizing Usability Issues in Games -- The Design of Buttons in MMO Mobile Game's Battle Interface -- esearch on the Quantization of User Experience of Spectator Mode in Moba Games -- Computer-Aided Games-Based Learning for Children with Autism -- Analysis of the Competitiveness of Asymmetric Gamesin the Market -- A Systematic Review of the Effect of Gamification on Adherence across Disciplines -- An Exploration of the Fear of Attack Strategy in Chess and its Influence on Class-A Players of Different Chess Personalities: An Exploration Using Virtual Humans -- The Factorial Structure and Underlying Contributors of Parents' Behavioral Involvement in Children's Video Game Use -- In-Game Virtual Consumption and Online Video Game Addiction: A Conceptual Model -- Player Types and Game Element Preferences: Investigating the Relationship with the Gamification User Types HEXAD Scale -- The Foundations and Frontiers of Research on the Effect of Video Games on Child Development: A Scientometrics and Knowledge-Mapping Analysis Based on CiteSpace -- Using Neural-Network-Driven Image Recognition Software to Detect Emotional Reactions in the Face of a Player while Playing a Horror Video Game -- Exploratory and Confirmatory Factor Analysis of the Chinese Young Children's Video-gaming Questionnaire -- Using Multiple Data Streams in Executive Function Training Games to Optimize Outcomes for Neurodiverse Populations -- Gameplay as Network: Understanding the Consequences of Automation on Play and Use -- Hitboxes: A Survey about Collision Detection in Video Games -- Adaptive Gamification and its Impact on Performance -- Designing Interactive Storytelling Games to Teach Computational Thinking -- In-Game Advertising: Brand Integration and Player Involvement as Key Influencing Factors on Brand Recall -- Detecting Real-Time Correlated Simultaneous Events in Microblogs: The case of Men's Olympic Football -- UNITY-Things: An Internet-of-Things Software Framework Integrating Arduino-Enabled Remote Devices with the UNITY Game Engine -- The Effects of Vibration on Assisting Game Play and Improving Player Engagement when Lacking Sound -- Investigating the Impact of Task Significance on Task Engagement and Enjoyment in Digital Games.

This two-volume set LNCS 12789 and 12790 constitutes the refereed proceedings of the Third International Conference on HCI in Games, HCI-Games 2021, held as part of the 23rd International Conference, HCI International 2021, which took place in July 2021. Due to COVID-19 pandemic the conference was held virtually. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The papers of HCI-Games 2021, Part I, are organized in topical sections named: Experience Design in Games; User Engagement and Game Impact; Game Mechanics.