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kikill's News

Posted by kikill - June 9th, 2021


An Interview with Raph Koster on Designing a COVID-10 Sim


Posting my questions and Raph Koster's replies (dated September 30, 2020 via email) as part of the documentation of "In the Time of Pandemia."


Khail: Could you describe how you went about crafting the game design sketch that became the basis of "In the Time of Pandemia" (ITOP)?

 

Raph: In early March of this year, I was spending a lot of time trying to educate people online about how viruses spread, why social distancing mattered, how deadly Covid might be… literally hours and hours arguing on social media. And people just didn’t get it. They had trouble picturing exponential growth (which is known to be a classic human cognitive challenge). They had trouble understanding the concept of repeated exposure, and how it pushed up the odds they would catch it.

 

Worse, they were really misunderstanding the tradeoffs on costs of lockdowns versus deaths. After all, epidemiology tells us that if everyone in the entire planet just stayed home and saw absolutely no one else for six weeks, the entire epidemic would be over.

 

I thought to myself, you know, if they played a game about this where they were put in the position of managing things, their process of optimizing for a high score would naturally lead them to certain conclusions.

 

But I didn’t have time to actually implement this. I have a new startup company, and we were dealing with the day to day impact of managing lockdown, our milestones, and all the rest. So I ended up just doing the design sketch and posting it on Facebook.

 

Khail: What were the challenges you encountered and how were you able to solve them?

 

Raph: The biggest was just picking the right variables to represent without making the whole thing over-complex. For example, at first, “diagnosed” was a state, a level of how sick you were. But commenters on the thread pointed out that a patient could die without ever being diagnosed, and a patient might also recover without being diagnosed, so I added a separate axis for it. I was very reluctant to add too many different axes to the game, because epidemiology is actually very subtle and complex.

 

Khail: Given the complexity of the SARS-CoV-2 pandemic, how were you able to pinpoint the elements to focus on?

 

Raph: It was all about the key lessons I wanted players to think about. Asymptomatic transmission was basically “the enemy” along with the length of the period in which people are contagious. The cost of lockdowns and the cost of testing. I wanted it to be a direct conflict between money and lives.

 

From there, the choices fell out pretty naturally. It led very naturally to things like including comorbidities, since one of the things that people were not clear on was the relative levels of risk for different people. Getting that across meant that I had to make the little colored circles in the sketch feel like people, so that there was some emotional impact to it. That’s why they have names, and not just ages and health stats.

 

Khail: Considering the real suffering associated with the subject, how were you able to ascertain that players would appreciate the resulting game? (An early tester rocked us a bit by saying, "I play games for escapism and not to be reminded of the impending pandemic." ITOP's average rating did end up in the top 3% of 224 simulators accepted by the Newgrounds community so far this year.)

 

Raph: Players can easily get turned off by a fantasy that isn’t something they want to engage in, and certainly, in stressful times many people prefer escapism. But I knew that plenty of people were obsessively following sites like the Johns Hopkins map, so I figured people like that were likely to be interested. Giving players a sense of control over the situation, where the real world very much left us all feeling like we had no control, seemed like it would also make a big difference.


Khail: A major factor why we were able to develop ITOP despite the limited time, zero budget, and no experience in the genre was that we had high confidence that the design you outlined was going to work. We were able to skip a significant amount of trial and error that comes naturally with a new game design. How could we generalize the game design process you described for resource-challenged contexts such as game dev start-ups, student capstone projects, and university research?


Raph: When I create game designs from scratch, I’m basically trying to create the sort of complex intersection of mathematical curves that something like a pandemic naturally has. I mean, if you think about the pandemic and the math of epidemiology, it’s very much a complex puzzle.

 

  • You have limited resources to take action. This is literally money, and of course, we put money in games all the time as a resource.
  • You also are working against the clock; the slower you take action, the more things happen, so you face time pressure, which is a classic game element.
  • You have a “landscape” that is the population, which is basically a complex moving graph of connections. Game designers often look at social webs as graphs of connections, but we also look at level design that way. You can abstractly think of the little circles changing color as they change state as being the same thing as turning nodes on a graph to different colors – which how a game of capturing territory, like Othello, works.
  • The disease makes “moves” of its own, captures some of that territory, and it has hidden information (you can’t tell which territory it has captured, not until the dot changes color so you know it is sick). That kind of hidden information is just like your hand in poker, secrets that the player is trying to deduce.
  • And of course, we give players tools they can spend their resources on. Since time, hidden information, and territory capture are the “tools of the opponent,” we give tools that counter each one: you can try to slow down time with lockdown, to uncover the “map” or hidden information using tests, and to recapture territory by hospitalizing.

 

This sort of abstract way of thinking is how I approach game systems design, and it’s a very powerful way of arriving at systems that will work. Once you have built this “machine” to speak, it’s easy to add small variations. It is also very important to tune the numbers – you can have a great machine, but with bad numbers the game could end up unplayable. In the case of the sketch, I actually started with the best available real world numbers at the time.

 

It’s also easy to think about how the player learns from what they are seeing. For example, asking yourself the question “how does the player learn about the captured territory?” In this case that’s the stages of sickness that the infected citizens go through. You want there to be a signal to the player about the severity, how fast it’s happening, where they can play defense. At that point, it’s about the user experience, and even the initial sketch I wrote had a lot of UX design elements in it, focused on teaching the player what the system was doing under the hood.

 

Khail: For [the last set of questions], we take ITOP to be an instance of game-based learning or educational games. The latter two terms are here treated as interchangeable.

 

Recent meta-analyses of game-based learning find that it is indeed more effective than traditional methods in terms of cognitive outcomes. However, not quite in agreement with the early optimism of advocates, the effect sizes thus far are less than moderate. As crucial, many studies show that game-based learning is not more motivating than conventional means. What is your take on this issue?


Raph: I think that any studies down those lines really need to have an expert game designer come in and evaluate the games used for the study to see if they are any good! There is a lot of terrible game-based learning content out there.

 

Khail: Among Newgrounds' top games of the day for August 2020, ITOP ranks 16th out of 28 games. Being able to stand toe-to-toe with top-rated games mostly built for entertainment can be considered as a counterexample for the claim "educational games fail as games". What do you think ITOP did right?

 

Raph: The overall game presentation is solid, the mechanics are fairly easy to learn, and the actual pacing – which is critical – is at the right speed for players to be able to pick up on what is going on. The right amount of “dressing” is there – meaning, audio and visual elements that make it not feel like a dry simulation. Players need that in order to make the feedback the game gives them feel rewarding.


Khail: Any ideas on how to improve the cognitive and motivational outcomes of educational games?

 

Raph: Educational games teach best when the lesson they teach is not mandatory, not the point of the game, but simply the best strategy for solving the problem. Players arrive at the strategy by trial and error. They persuade themselves, and teach themselves, because it’s the way to beat the game. But way too much game-based learning material instead makes the lesson the point of the game, or an obstacle to be overcome. The fun is then just small bits of reward for basically doing homework. That is rarely fun, and experts in the field call this “chocolate covered broccoli.”


***


Thank you, Raph, for sharing with us your insights and for providing us with the inspiration and opportunity to serve our communities in the time of pandemia.


-- Khail Santia, ITOP Lead Game Developer


Posted by kikill - June 28th, 2020


These notes expand on the guide embedded in the game to: (1) describe the determination and usage of the main parameters, (2) outline some limitations, and (3) list down references.


Zones 1 to 5 essentially compose a difficulty ramp leading to Zones 6 and 7. The latter two hew closest to real-world data. Zone 8 leans more towards a subjective description of what the threat of COVID-19 is like in areas with hyper-concentrated density.


Parameters


The detailed parameters of Zones 2 to 8 can be seen in the Sandbox Editor in Zone 9.


Transmission Risk


"Transmission risk" is defined here as the probability of contracting the virus on contact with an infected person. "Contact" in turn is defined in [1] as a meeting involving face-to-face conversation or touch. The transmission risk in the real world is roughly estimated at 1% from [2] and [3]. To translate that into the game, the mean daily contacts in [1] (12.5 contacts per person per day) is divided by the mean daily contacts in Zones 6 and 7 (0.35 contacts per person per game day) multiplied by 1%. That's 12.5 / 0.35 x 1% ≈ 36% transmission risk. Seen another way, one contact event in Zones 6 and 7 is taken to represent ~36 real-world contacts.


Transmission Risk Modifiers


Masking in non-healthcare settings—where medical-grade masks are less common—is associated with an aggregated relative risk of 56% [4], translated in the game as reducing the transmission risk by 44%. Eye protection such as goggles and face shields are associated with an overall relative risk of 34% [4], interpreted in the game as reducing the transmission risk by 66%. Hand washing reduces risk of infection by 24% [5]. Social distancing of one to two meters is associated with an overall relative risk of 30% [4], implemented in the game as activating contact avoidance 70% of the time.

 

Disease Progression


The probabilities for progression from one state to the next is based on the case severity distribution in [6] with the proportion of asymptomatics checked with data from [7]. The various periods of the progression are based on [8], [9], and [10] as summarized in [11]. and supplemented by [12] for the estimated length of the critical period. The interpretation in the game is as follows: 81% of asymptomatics progress to symptomatic in two to 14 days. 17% of symptomatics progress to severe in five days. 29% of severe patients progress to critical in another five days. Finally, 49% of critical patients expire in eight days. Infected townsfolk who do not expire recover after 20 to 32 after contracting the virus.


Progression Modifiers


In the game, there are two sources of progression modifiers (or risk factors)—comorbidities (MCs) and age (MAs). The list of comorbidities, their respective case fatality rates (CFRs), and CFRs by age group are taken from [6] and buttressed by [13], [14], and [15].


MCs are factors that increase the probability of the disease worsening. To obtain those, the CFR of each comorbidty is dividied by the CFR for no underlying condition. The MCs are used in the following way. The probabilities of progression from symptomatic to severe, from severe to critical, and from critical to dead are each multiplied by the cube root of the MC relevant to a given individual. This is to distribute the MC across the three mentioned stages while keeping its overall effect. The prevalence of comorbidities are drawn from [16], [17], [18], [19], and [20] representing global figures that are then applied to the population in the game.


MAs either increase or decrease the probability of the disease worsening. Older individuals tend to have higher risk and younger individuals lower. To obtain the MAs, the CFR of each age bracket is divided by the CFR for 50-59 year olds. The MAs are then used in the same manner as the MCs above. The effect of MCs and MAs is cumulative.


Hospital Beds


The world has about three hospital beds per 1000 people [21]. Countries with a bed capacity of one per a hundred people are rare. ICU beds are even fewer (for instance in [22]). A possible justification for making more ICU beds available in the game is the recent ramping up of hospital resources. Still, the actual number of ICU beds is unlikely to reach one per 100 people for most communities.


Economy


The daily revenue from each townsfolk in the game adds up in one year to about 22% of the average annual salary in Cebu City, Philippines [23] where the game is being developed. This revenue can be treated as taxes paid by the townsfolk (as income tax, sales tax, and others). The initial funds for Zones 2 to 5 are about equal to each zone's respective income in six months before the pandemic; it's one-third of the expected income in the same period for Zones 6 to 8.


Each Coronavirus test kit in the game costs the town $37 (from [26]). The town spends a token $1 to administer a test. Isolating or quarantining an individual costs the town $8 a day, about equal to the minimum wage. Lastly, hospitalization for each COVID-19 patient costs the town $861—computed by taking the average of the compensation for severe pneumonia cases and critical cases in [28] divided by 13 days (the period of hospitalization in game time).


Limitations


Many aspects of the simulator can be improved. Some limitations then, in addition to those already identified, will be mentioned for future work.


The first is that human beings are not gas molecules that bounce around randomly. Humans too can exchange information such as to avoid certain areas with known incidence of infection.


The second is that basing the probabilities of disease progression on the severity distribution in [6] could be a crude estimate at best of the actual probabilities. Although the data in [6] consists of a large sample of more than 72,000 patient records from China that covers a period of about two months, it still remains the case that severity distribution is not exactly the same as disease progression. Moreover, many asymptomatic cases could have been undetected.


The third limitation I will point out is the oversimplification in the game's uniform risk of transmission throughout the period of infection when evidence points to viral load—and hence, transmission risk—peaking five to six days after the onset of symptoms then subsiding after [26].


Fourth, the porosity parameter, which corresponds to transmission from outside town, is implemented in quite a contrived manner. Setting the porosity to moderate in Sandbox Mode, for example, a new infection appears whenever the incidence drops to zero until the six-month limit is reached.​


Fifth, the comorbidities are distributed among the population regardless of age or sex.


Sixth, the comorbidities documented in [6], [13], and [15] were observed from Chinese patients which exclude a comorbidty frequently mentioned elsewehere (such as in [29]), namely, obesity.


Seventh, the CFRs of patients in [6], [13], [14], and [15] already account for comorbidities and age. Extracting progression modifiers from these studies may magnify the effect of comorbidites on CFRs. Although MAs may balance out the net effect as they point in opposite directions.


Eighth, a similar magnification of effects could also result from the transmission risk modifiers.


Despite the possible distortions in the previous two limitations, keeping the modifiers in the game is still considered valuable as they show, for example, how better hygiene can save lives as well as how those with pre-existing conditions or advanced age need extra protection. Caution is of course warranted in interpreting the numbers coming out of the game.


The ninth limitation is that the simulator does not have the equivalent of law enforcement. Townsfolk who refuse to comply with quarantine cannot be compelled to.


And tenth, the game economy can be fine-tuned in many places. For instance, everyone is considered able to generate income even those not of working age. Also, there is no mechanism for borrowing money. Still another is that tax collection occurs daily contrary to usual practice.

 

References


[1]       K. O. Kwok et al., "Temporal variation of human encounters and the number of locations in which they occur: a longitudinal study of Hong Kong residents," J. R. Soc. Interface, vol. 15, no. 20170838, Jan., 2018. doi: https://dx.doi.org/10.1098/rsif.2017.0838.


[2]       M. A. Otto, "COVID-19 update: Transmission 5% or less among close contacts," Hospitalist, Mar. 11, 2020. [Online]. Available: https://www.the-hospitalist.org/hospitalist/article/218769/coronavirus-updates/covid-19-update-transmission-5-or-less-among-close


[3]       H. Cheng at al., "Contact tracing assessment of COVID-19 transmission dynamics in Taiwan and risk at different exposure periods before and after symptom onset," JAMA Intern. Med., May, 2020. doi: https://dx.doi.org/10.1001/jamainternmed.2020.2020.


[4]       D. K. Chu et al., "Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis," Lancet, Jun., 2020. doi: https://dx.doi.org/10.1016/S0140-6736(20)31142-9.


[5]       T. Rabie and V. Curtis, "Handwashing and risk of respiratory infections: a quantitative systematic review," Trop. Med. Int. Health, Mar., 2006. doi: https://dx.doi.org/10.1111/j.1365-3156.2006.01568.x.


[6]       The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team, "The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19)—China 2020," China CDC Weekly, vol. 2, no. 8, Feb., 2020. doi: https://dx.doi.org/10.46234/ccdcw2020.032.


[7]       M. Kenji et al., "Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020," Eurosurveill. 2020, vol. 25, no. 10, Mar. 12, 2020. doi: https://dx.doi.org/10.2807/1560-7917.ES.2020.25.10.2000180.


[8]       Center for Disease Control and Prevention, "Symptoms of Coronavirus," Center Disease Control Prevention, May, 2020. [Online]. Available: www.cdc.gov/coronavirus/2019-ncov/about/symptoms.html


[9]     D. Wang et al., "Clinical characteristics of 138 hospitalized patients with 2019 Novel Coronavirus–infected pneumonia in Wuhan, China," JAMA 2020, vol. 323, no. 11, Feb. 7, 2020. doi: https://dx.doi.org/10.1001/jama.2020.1585.


[10]     X. Jiang et al., "Towards an artificial intelligence framework for data-driven prediction of coronavirus clinical severity," Comp. Mat. Continua, vol. 63, no. 1, Mar. 30, 2020. doi: https://dx.doi.org/10.32604/cmc.2020.010691.


[11]     A. Bendix, "A day-by-day breakdown of coronavirus symptoms shows how the disease COVID-19 goes from bad to worse," Bus. Insider, Apr., 2020. [Online]. Available: https://www.businessinsider.com/coronavirus-covid19-day-by-day-symptoms-patients-2020-2


[12]     Health Information and Quality Authority, "Evidence summary for average length of stay in the intensive care unit for COVID-19," Health Inf. Qual. Authority, Smithfield, Dublin, 2020. Available: https://www.hiqa.ie/sites/default/files/2020-04/Evidence-summary_Covid-19_average-LOS-in-ICU.pdf


[13]     F. Caramelo et al., "Estimation of risk factors for COVID-19 mortality—preliminary results," medRxiv, Feb. 25, 2020. doi: https://dx.doi.org/10.1101/2020.02.24.20027268.


[14]     J. Oke and C. Heneghan, "Global Covid-19 Case Fatality Rates," Centre Evidence-Based Med., Jun., 2020. [Online]. Available: https://www.cebm.net/covid-19/global-covid-19-case-fatality-rates/


[15]     Center for Disease Control and Prevention, "Interim Clinical Guidance for Management of Patients with Confirmed Coronavirus Disease (COVID-19)," Center Disease Control Prevention, Jun., 2020. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-guidance-management-patients.html


[16]     G. A. Roth et al., "Global, regional, and national burden of cardiovascular diseases for 10 Causes, 1990 to 2015," J. Am. Col.l Cardiol., vol. 70, no. 1, Jul., 4, 2017. doi: https://dx.doi.org/10.1016/j.jacc.2017.04.052.


[17]     P. Saeedi et al., "Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes Federation Diabetes Atlas, 9th edition," Diabetes Res. Clin. Pract., vol. 157, no. 107843, Nov. 1, 2019. doi: https://doi.org/10.1016/j.diabres.2019.107843.


[18]     M. Xie et al. "Trends in prevalence and incidence of chronic respiratory diseases from 1990 to 2017," Respiratory Res., vol. 21, no. 49, Feb. 11, 2020. doi: https://doi.org/10.1186/s12931-020-1291-8.


[19]     World Health Organization, "Hypertension," World Health Organization, Sept. 13, 2019. [Online]. Available: https://www.who.int/news-room/fact-sheets/detail/hypertension


[20]     F. Bray et al., " Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries," CA: Cancer J. Clinicians, vol. 68, no. 6, Sept. 12, 2018. doi: https://doi.org/10.3322/caac.21492.


[21]     The World Bank, "Hospital beds (per 1,000 people)," World Bank, 2020. [Online]. Available: https://data.worldbank.org/indicator/SH.MED.BEDS.ZS


[22]     UP COVID-19 Pandemic Response Team, "Estimating Local Healthcare Capacity to Deal with COVID-19 Case Surge: Analysis and Recommendations," University Philippines, Apr., 2020. [Online]. Available: https://www.up.edu.ph/estimating-local-healthcare-capacity-to-deal-with-covid-19-case-surge-analysis-and-recommendations/


[23]     PayScale, "Average Salary in Cebu City, Philippines ₱249k," PayScale, 2020. [Online]. Available: https://www.payscale.com/research/PH/Location=Cebu-City/Salary


[24]     National Wages and Productivity Commission, "Region VII (Central Visayas) Daily Minimum Wage Rates," Nat. Wages Productiv. Commission, 2019. [Online]. Available: https://nwpc.dole.gov.ph/regionandwages/region-vii-central-visayas/


[25]     Department of Finance National Tax Research Center, "Where Does Your Tax Money Go?," Dept. Finance Nat. Tax Res. Center, Jun., 2015. [Online]. Available: http://www.ntrc.gov.ph/images/Publications/where-does-your-tax-money-go.pdf


[26]     C. J. M. Gonzale, "UP NIH Spinoff begins mass distribution of DOST Pinoy-made COVID-19 test kits," Phil. Council Health Res. Develop., Apr., 2020. [Online]. Available: http://www.pchrd.dost.gov.ph/index.php/news/6537-up-nih-spinoff-begins-mass-distribution-of-dost-pinoy-made-covid-19-test-kits


[27]     PhilHealth, "PhilHealth guarantees continuing coverage for Covid-19 patients," PhilHealth, Apr., 2020. [Online]. Available: https://www.philhealth.gov.ph/news/2020/cont_coverage.php


[28]     A. Tamara and D. L. Tahapary, " Obesity as a predictor for a poor prognosis of COVID-19: A systematic review," Diabetes Metab. Syndr., Vol. 14, no. 4, July-August, 2020. doi: https://dx.doi.org/10.1016/j.dsx.2020.05.020.