Table 2.

Identified HMD-VR health games and summary including technology implementation, health context, and game design. Mechanics-Dynamics-Aesthetics framework sumarizes game design. Motivation describes authors' explicit and specific association of theory and design with motivation or engagement beyond the ubiquitous “immersive games are motivating”. Guidance describes features that help instruct the player through the gameplay experience. NS refers to game design aspects Not Specified in the article, including common features such as rewards (points, badges, etc.) and narrative (story, theme, characters, etc.); this does not imply such elements are necessary game design features

Author	Year	Display and interaction technology	Intended health context and end-users	Game design summary
Gobron et al. [50]	2015	HMD + Lower Limb Haptic Robot	Lower limb rehabilitation for post-stroke patients; varied ages from kids to seniors	Four mini games with limited detail Gate Crossing M: Use feet to pilot spaceship through gates A: “Young space pilot learning to use a spaceship” BikeRehab M: Pedaling; pizza to deliver; obstacles in path; 2D side-scrolling world; score A: Be a great pizza delivery boy BeTheBall M: Leg press to move ball; “ghost” of best performance A: Racing through different outdoor environments as a ball, challenge to get highest score PicsWalk M: Walking motion to navigate; take photos A: Being a photographer walking through a beautiful forest full of wildlife and plants Motivation: Users motivated by playing games of interest NS: Narrative, Guidance
Shaw et al. [55]	2015	HMD + Skeletal Tracking + Cycle	Physical exercise for sedentary/overweight adults (implicit)	Cycling Obstacle Course M: Cycling forward and steering using body leaning through a branched course with more or fewer obstacles and reward objects; scoring based on speed, distance, and rewards collected; fixed number of lives D: Tensions between choosing speed vs avoiding obstacles and risk vs reward A: Overcoming a challenging obstacle course as fast as possible Motivation: Based on challenge, scoring, moment-moment choice in branches, non-repetitive play Guidance: Game explained by researchers NS: Narrative
Gromala et al. [48]	2016	HMD	Pain relief for persons with acute and chronic pain	Mobius Floe M: movement along a “rail” path, encounters with hostile “Neuron Trees” and helpful characters to interact with; varied projectiles; health packs and health points; shoot medication with different effects D: Defend against neuron trees in a “time-sensitive manner”; measured use of medication on Neuron Trees A: Be immersed and journey through an exciting snowy world; overcome challenges symbolizing pain experiences Motivation: The multisensory experience with high interactivity and thematic narrative helps to achieve immersive engagement; health points motivates focus on game tasks Guidance: In-game tutorial
Ijaz et al. [63]	2016	HMD + Skeletal Tracking + Cycle	Older vs younger adults and physical exercise	Two variants of a game: competitive, affiliative M: City environment with a map, compass, and using pedalling to navigate; competitive version involves guessing landmarks, scores based on performance, leaderboard, and levels; affiliative version involves audio descriptions of landmarks, taking photos, and a photo album D: Competitive: plan efficient route, predict landmarks, beat own/others’ scores, explore the city Affiliative: go to all landmarks, craft collection of photos A: Competitive: find your way in a strange city and be the best at it; Affiliative: Being a cycling tourist Motivation: Based on self-determination theory; competitive vs affiliative play Guidance: In-game tutorial NS: Narrative
Lv et al. [65]	2016	HMD + Microphone	Persons with dysphonia/presbyphonia	Space Flight Game M: Voice pitch and loudness controls elevation of a spaceship moving amongst planets as obstacles; score at end D: Avoid planets as long as possible A: Steering a 2D side-scrolling spaceship Guidance: Clinician guidance NS: Motivation, Narrative; vague mention of “game stories”
Thomas et al. [71]	2016	HMD + Skeletal Tracking (marker-based)	Movement promotion for persons with kinesiophobia	Dodgeball Game M: Player holding ball on dodgeball court against opposing computer players who launch balls at player at variable heights; incoming balls are coloured to indicate action to block or dodge; scoreboard D: Focused on reacting quickly to block or dodge, pre-positioning, beating own score A: Be an untouchable dodgeball player; improve at dodging and blocking Guidance: practice level to introduce mechanics NS: Motivation, Narrative
Tuveri et al. [49]	2016	HMD + Skeletal Tracking + Cycle	Physical exercise for a general audience (implicit)	Rift-a-bike M: Player pedals at varying speeds through three levels of a city bike tour: warm-up, exercise, cool-down; players rewarded with experience, skill, and karma points for performance and actions; challenge missions present objectives; Rabbit to follow; coins along cycling path D: Chase the rabbit and collect as many coins as possible. Complete missions A: A city cyclist taking on missions that make up the “game plot”; challenge of improving your score. Build your prize collection Motivation: Reward mechanics provide motivation for playing; rabbit is a persistent objective and relative position provides performance feedback NS: Guidance
Howes et al. [75]	2017	HMD + Skeletal Tracking	Strength and balance training for older adults at risk of falling	Several Minigames; limited detail NS: Motivation, Rewards, Narrative, Guidance
Nielsen et al. [67]	2017	HMD + Hand Motion Controllers	Persons with lower limb amputation and phantom limb pain	Two games; limited detail Shape Game M: foot positioning tracked by controller strapped to feet, incoming shapes, and points awarded for matching feet position to shape Slingshot Game M: Slingshot manipulated using feet, targets to shoot, points awarded NS: Motivation, Narrative, Guidance
Ambron et al. [58]	2018	HMD + Lower Limb IMU Sensors	Persons with lower limb amputation and phantom limb pain	Three games adapted: Chess, Checkers, and Quest for Fire Quest for Fire M: Boxes and other objects for overcoming obstacles in each level of a labyrinth D: Players could create the best routes for navigating through the labyrinth A: Escape the labyrinth Motivation: Authors used “rich virtual environments” to increase motivation NS: Rewards, Narrative, Guidance not specified
Avola et al. [56]	2018	HMD + Skeletal Tracking + Hand Tracking	Upper limb rehabilitation for persons with neuromotor impairments	VRheab, limited detail Some mechanics involving finger pinching and raising knees NS: Rewards, Narrative, Guidance
Caggianese et al. [53]	2018	HMD	Cognitive training for persons with Alzheimer’s disease and mild cognitive impairment	Activities of Daily Living based scenarios involving motion and memory tasks; limited detail Motivation: Customized difficulty level by clinician and encouragement to do tasks on their own Guidance: Clinician guided NS: Rewards, Narrative
Czub and Piskorz [59]	2018	HMD	Treatment of acute pain	M: Sphere avatar, steering, obstacle red sphere, reward white sphere D: Collect as many points as possible by hitting white spheres and avoiding red spheres A: Challenge of getting a high score Guidance: practice phase of experiment NS: Motivation, Narrative
Eisapour et al. [78]	2018	HMD + Hand Motion Controllers	Physical Exercise for persons with dementia	Untitled Exergame M: Interactions based on neck, shoulder, and arm movement; tasks involving objects to reach for and place; placing tasks adjustable for range of motion; farm-related objects D: Four scenarios: follow the butterfly with head; lift apple boxes; sort fruit; row the boat A: Doing calm things on a pleasant farm Guidance: Pre-recorded instructions for each scenario and task NS: Motivation, Rewards, Narrative
Huang et al. [61]	2018	HMD + Robotic Arm	Upper Limb Rehabilitation (Stroke)	SpaceWar 3D M: Control spaceship position; incoming meteorites; shoot missiles; enemy spaceships; score based on time and number of enemies shot down D: Dodge meteorites, target and shoot spaceships; tensions between avoiding collisions and targeting enemies A: Being an ace space combat pilot Motivation: Dynamic objects and audio as feedback that increases engagement NS: Guidance, Narrative
Lee and Kim [64]	2018	HMD	Binocularity stimulation for children with residual amblyopia	Ice Cream Truck M: Running kids; throwable ice cream; difficulty level D: Hit as many kids with ice cream as you can A: Feeding all the kids ice cream NS: Motivation, Rewards, Narrative, Guidance
Mihajlovic et al. [66]	2018	HMD	Neck Pain Rehabilitation	Untitled Exergame; multiple scenarios M: Track objects with head motion; butterfly target; net to catch butterfly; score based on caught butterflies and movement quality; different levels D: Catch as many butterflies as possible, quickly and accurately A: Be a butterfly catcher in realistic indoor environments Motivation: Realistic immersive environment with butterfly as objective and feedback NS: Narrative, Guidance
Piskorz and Czub [68]	2018	HMD	Acute Pediatric Pain and Stress	Untitled game based on “Multiple Object Tracking paradigm”; limited detail M: Flashing elements, scenes where flashed elements are located, head movement to control game; difficulty level D: Memorize and find the flashed elements Guidance: Two 10–15 min training scenes NS: Rewards, Narrative
Proffitt et al. [69]	2018	HMD + Skeletal Tracking	Stroke Motor Rehabilitation (Full body)	Mystic Isle M: Avatar; different coloured bottles of varied heights; bin and button for filling; garbage bags; conveyor belt D: Sort bottles into correct bins; fill bottles completely without overflowing; load bags onto hooks A: Become an efficient recycler NS: Motivation, Narrative, Guidance
Sisto et al. [54]	2018	HMD + Skeletal Tracking	Posture and Preventing Musculoskeletal Disorders	Untitled Serious Game; game and level design explicitly addressed M: Puzzle board with pegs and replaced gears; gears to be selected and placed using hand movements; movement quality scoring; game score based on completion time D: Solve puzzle by selecting correct gears; tension between minimize time vs movement quality A: Spaceship and robot theme; solving puzzles Motivation: balancing game difficulty and cognitive load; not to hard/easy for engagement NS: Narrative, Guidance
Dias et al. [60]	2019	HMD + Markerless Hand Tracking	Upper limb rehabilitation for post-stroke patients	A Priest in the Air M: Steer hot-air balloon using arm and wrist position/rotation; obstacles; stars to collect; branching paths; difficulty selection; different biome environments; King’s Castle at the end D: Travel through different environments to reach the King’s Castle; maximize stars/points collection A: Player vs environment challenge; challenge improving overall high score; soaring through the air in a hot air balloon travelling the world; story set by opening and closing cutscenes with characters Priest, Dog’s Priest, King Motivation: defined by short, mid, and long-term goals; adjustable game difficulty Guidance: Explicit usability consideration; tutorial videos; help icons in-game
Ijaz et al. [62]	2019	HMD + Cycle	Physical exercise for a general audience (implicit)	Pokemon Ride M: Navigation via pedalling/steering through city with map and different locations and levels; pokemon at different locations to catch; score based on pokemon type; physiological feedback D: Find all the pokemon A: Collection and accumulation; collecting together with others but individually Balloon Shooter M: Similar map/navigation; different weapons for shooting balloons placed around map; points for shooting balloons D: Keep shooting balloons to unlock levels A: Be a crackshot balloon hunter in the city Motivation: based on Self-Determination Theory Guidance: in-game tutorial NS: Narrative
Nehrujee et al. [76]	2019	HMD	Rehabilitation for patients with vestibular dysfunction	Cardboard Break M: Head movement pitch/yaw based on vestibular training; reticle to aim at cardboard boxes that randomly appear with varied distance from centre; score by moving reticle onto box; countdown timer; adaptive difficulty D: Gaze shift to box as quickly as possible A: Challenge of getting a high score Follow Me M: Continuously moving ball; trials; score based on head tracking ball; adaptive difficulty D: Track the ball with your head for as long as possible A: Challenge of getting a high score Motivation: Adaptive algorithm to adjust difficulty to achieve state of flow NS: Narrative, Guidance
Rossi et al. [70]	2019	HMD	Treatment for persons with Sensory Processing Disorders	Imaginator; two scenarios, four tracks, three activities M: Rail and cart moving; different coloured moving balls, letters, and numbers; clinician sets task objective; player uses gaze to make selections; score based on correct selections; variable difficulty D: Hit the correct moving ball; hit moving letters in correct pattern; select correct sum A: Pleasant roll on tracks in an outdoor park Guidance: Clinician guided NS: Narrative; recommended to have future character interaction
Tong et al. [51]	2019	HMD + Hand Motion Controllers	Physical exercise for persons with arthritis	Lumapath M: Motion-based gestures aimed at arthritis physical activity; ship to drive; different planets; various plants and life forms of rarity; floating patter of dots to follow with gestures; teleportation to move through world D: Explore the planets; discover new things in environment; draw shapes following dot patterns A: Take your personal ship to explore different planets Guidance: 10 min tutorial; thematic analysis revealed participants would like more guidance through the experience NS: Motivation (thematic analysis revealed exploration played major role in motivation), Rewards, Narrative
Yao and Kim [72]	2019	HMD + Cycle	Physical exercise for a general audience (implicit)	VIR Zoom (commercialized); limited detail NS: motivation, rewards, narrative, guidance
Yaramothu et al. [73]	2019	HMD	Vision therapy for convergence insufficiency	VERVE (Virtual Eye Rotation Vision Exercises); limited detail M: convergence related mechanics NS: motivation, rewards, narrative, guidance
Xu et al. [20]	2020	HMD + Skeletal Tracking	Physical exercise for sedentary individuals	GestureStar M: blocks flying towards player; varied patterns of blocks requiring gestures of different workloads D: perform correct gesture just as block reaches you A: similar to commercially available rhythm and music games NS: motivation, rewards, narrative, guidance
*Barathi et al. [57]; Farrow et al. [52]	2018, 2019	HMD + Cycle	Physical exercise for sedentary individuals	Untitled Exergame explicitly designed according to MDA Framework M: cycling and steering; prompts and pattern of speed and resistance changes following HIIT (High Intensity Interval Training) with environmental changes; truck obstacles; best performance ghost; countdown timer D: maximize accomplishment in limited time; follow the HIIT protocol; race against yourself A: self improvement; cycling in traffic; nice sunny ride vs exciting night race Motivation: discussed in terms of intrinsic motivation and interactive feedforward method Guidance: instruction sheet about experiment and exergame NS: rewards, narrative

*These two articles describe the same HMD-VR health game. The outcomes were combined