## 2 Materials and Methods
### Study Design and Enrollment  
The experimental procedure was approved by the Institutional Review Boards (IRB) of the University of Massachusetts Amherst (IRB# 2018-4728) and Heeyeon Rehabilitation Hospital, and the approved clinical trial was registered (ISRCTN10613029). As it was the first clinical trial on _Neuro-World_ with post-stroke survivors, the sample size was computed conservatively, aiming for the minimum effect size of \(f=0.2\), significance level of \(\alpha=0.05\), and statistical power of \(\beta=0.8\). The computed target sample size was 50. We recruited stroke survivors among those who had been institutionalized in the Nursing Center at Heeyeon Rehabilitation Hospital in South Korea, a long-term care facility for individuals with chronic disorders. Participant recruitment was open for one month until the targeted number of patients was met. To be included in the study, participants had to be at least two years post-stroke since most stroke survivors in South Korea have the opportunity to stay in rehabilitation units for two years due to substantial subsidy by the public insurance. In addition, participants needed to score 18 points or greater on the Korean version of the Mini-Mental State Examination (MMSE) [45]. Exclusion criteria were the presence of any issues that could affect the self-operation of _Neuro-World_, such as physically being incapable of using a mobile device independently (i.e., both limbs do not have the necessary motor function, indicated by the scores of 20 or less on the Manual Function Test [46]) and vision-related issues (e.g., visual neglect). Eligible participants were randomized to the control group (i.e., standard medical care) or the experimental group (i.e., standard medical care plus _Neuro-World_) using a random number generator. Baseline tests were completed one week before the first _Neuro-World_ session and post-intervention tests were completed one week after the last session for all the subjects by an experienced language pathologist (hereinafter referred to as _assessor_). The assessor was only involved in the pre- and post-intervention assessments and blinded to the participant group assignment.  
Participants in the experimental group used _Neuro-World_ for 30 min per day, twice a week (i.e., Tuesdays and Thursdays), for 12 weeks. In each 30-min session, participants spent five minutes on each of the six games. When the five minutes had elapsed for a given game (at any stage), users were automatically directed to another randomly chosen _Neuro-World_ game. When users reached the highest stage (i.e., stage 20) of a given game within the five-minute duration, stage 20 was repeated with randomized game-specific variables. On the days and times that participants agreed to play _Neuro-World_, research staff visited the experimental group participants to bring a 12.2-inch tablet computer (Galaxy Note Pro, Samsung) that was pre-installed with the Korean version of _Neuro-World_. However, the research staff members did not provide any assistance when the participants were using the system. Participants were allowed to freely choose where to play _Neuro-World_ (e.g., on their beds, couches, chairs in their room, or a lounge). The research staff collected the tablet computer when participants finished the suggested 30 min of _Neuro-World_. Participants in both groups received no additional cognitive or motor rehabilitation therapies other than standard medical care, which included routine checkups (e.g., blood pressure tests, diabetes screening) and/or any medically necessary treatments (e.g., decubitus ulcer).