A GAME ABOUT READING THE LINE
What is Extraplot?
Extraplot is a chart prediction game that turns time-series reading into a short, hands-on exercise. You see a real annual data series through a cut-off year, draw a continuation across the shaded area, and reveal the historical values that came next. Instead of choosing an answer from a list, you commit to a shape: a steady climb, a plateau, a dip, or a reversal.
Each Extraplot round uses attributed open data from the World Bank’s World Development Indicators or the Global Carbon Project. To keep different topics playable on the same chart, the source values are min–max scaled to a 0–100 index. The score compares the shape of your drawing with observed history; it is not a grade for real forecasting.
HOW IT WORKS
How to play the Extraplot game
Read the visible history
Follow the solid line up to the dashed year. Notice the direction, pace, and any turning points. The scale is a normalized index, so compare the curve within its own chart rather than reading the axis as the original unit.
Draw into the shaded area
Drag from the cut-off through the final year. A mouse, trackpad, or touch screen works. With a keyboard, focus the chart, use the left and right arrows to select a year, then use up and down to adjust your index value.
Reveal and compare
Reveal the actual historical line and compare it with your drawing. Extraplot reports your mean absolute miss in index points and calculates a point score as max(0, round(100 − 1.6 × average miss)). Reset at any time before reveal, or continue through all five charts to compare your session.
The game asks you to complete every hidden year so that your guess is a connected path, not a single endpoint. A drawing can be revised before reveal, and scores stay in the current browser session. Nothing is submitted as a personal forecast or saved to a profile.
FEATURES
A real-data chart guessing game with clear rules
Five open-data series
Practice with global internet use, GDP per person, forest cover, renewable energy, and CO₂ emissions. Every round shows its source, original unit, years, and reuse attribution in the data details.
Mouse, touch, and keyboard input
Draw a continuous line directly on the chart or make careful point-by-point adjustments with arrow keys. A visible cut-off, shaded future area, and progress markers keep each round easy to follow.
Transparent scoring
The result shows the average absolute miss in index points and the rule used to translate it into a game score: max(0, round(100 − 1.6 × average miss)). Sample forecast paths are generated from visible history and are labeled separately from real observations.
Extraplot runs locally in the page and starts a fresh set of five rounds when you reload. It does not ask for an account, send a forecast to a server, or imply that one line can explain why the underlying data changed.
USE CASES
Who can use a chart prediction game?
Students practicing data literacy
Students can use Extraplot as a short warm-up before a lesson on graph scales, outliers, and extrapolation. Ask learners to explain what clue led them to extend the trend or expect a change in direction.
Teachers leading a discussion
One class can draw several plausible continuations from the same history, then compare assumptions. A flat line, continued growth, and a reversal can all be reasonable guesses until new observations become visible.
Teams talking about trends
A product or research team can use a round to discuss whether a recent jump looks durable or temporary. Treat the activity as a conversation starter, then use validated evidence for decisions and planning.
Extraplot pairs well with other hands-on learning on ToolAtrium. Browse the interactive tool directory for more experiments, or use Learn Arduino to practice a different kind of step-by-step reasoning.
EXAMPLES
Three patterns to consider before you draw
Growth that begins to level off
If a rising curve has smaller steps near the cut-off, continuing a straight line may overshoot. You could instead draw a curve that approaches a ceiling. The internet-use round gives you a chance to compare these possibilities with later observations.
A long drift with a small annual change
Forest cover changes gradually in the selected series. The chart scales its full range to make the direction visible, so check the original unit in the source panel before interpreting the size of the change as a percentage-point difference.
A broad trend interrupted by a dip
GDP per person and CO₂ emissions include years when the line turns or falls. A trend can resume, pause, or reverse after a disruption. Draw the continuation you think is most plausible, then use the reveal to inspect what happened in the actual historical record.
These examples are prompts for reading the chart, not claims that a single pattern explains the future. The game scores your plotted points against a recorded series; your reasoning can still be thoughtful when the outcome is surprising.
OPEN DATA AND ATTRIBUTION
What data does Extraplot use?
The five rounds use annual world-level observations from 2005 through 2023. Four indicators come from World Bank World Development Indicators and their credited providers; the emissions series comes from the Global Carbon Budget. World Bank WDI indicators are licensed CC BY 4.0 unless their metadata states otherwise. The Global Carbon Project publishes its budget data under CC BY 4.0. Source names and license notes are repeated in each chart’s information panel.
To put different measurements on one chart, each series is linearly scaled between its lowest and highest value in the displayed period. The y-axis is therefore an index from 0 to 100, not the original unit. The hidden segment contains later historical values; it is not a generated prediction or live feed. Data providers update their series on their own schedules, so the page uses a reviewed snapshot and names the provider for each round.
- People using the InternetInternational Telecommunication Union, via World Bank World Development Indicators; processed by Our World in Data.World Bank WDI data is licensed CC BY 4.0; credit the ITU as the original provider.
- GDP per person around the worldNational statistical organizations, OECD, and World Bank staff estimates; processed by Our World in Data.World Bank WDI data is licensed CC BY 4.0; source providers are credited.
- Share of land covered by forestFood and Agriculture Organization of the United Nations, via World Bank WDI; processed by Our World in Data.World Bank WDI data is licensed CC BY 4.0; credit FAO as the original provider.
- Renewable energy in final energy useInternational Energy Agency, via World Bank World Development Indicators; processed by Our World in Data.World Bank WDI data is licensed CC BY 4.0; credit the IEA as the original provider.
- CO₂ emissions per personGlobal Carbon Budget 2026, Global Carbon Project; population series processed by Our World in Data.Global Carbon Project data is licensed CC BY 4.0; cite the Global Carbon Budget.
READ THE RESULT CAREFULLY
What a score can and cannot tell you
A close line means your drawn values stayed near the observed values in this particular time window. It does not prove that you know the cause of the trend or that the same approach will work on a different series. The point score is a playful summary of average index error; it is not a probability, forecast interval, or measure of professional skill.
The chart hides part of a known past record to make a fair guessing exercise. In real analysis, the next period has not happened yet and may respond to policy, technology, shocks, measurement changes, or other factors. Use the source metadata and original units before making any decision from a chart.
FAQ
Frequently asked questions about Extraplot
What is Extraplot?
Extraplot is a free chart prediction game. Draw how you think an observed data line continues, reveal the later historical values, and compare the shape of your guess.
How do I play the Extraplot game?
Drag through the shaded forecast area to the final year. You can also focus the chart and use arrow keys to choose a year and adjust the index. Reveal becomes available when every hidden year has been drawn.
Is Extraplot free to play?
Yes. The game is free in a modern browser, needs no account, and keeps scores only in the current page session.
Are the Extraplot charts real data?
Yes. The rounds use attributed open-data snapshots from World Bank World Development Indicators and the Global Carbon Project. Each chart’s information panel names its provider and license.
Why does the chart use a 0–100 index?
Each series has a different unit, such as percent of population or tonnes of CO₂ per person. Min–max scaling lets every round share the same drawing surface; the source panel retains the original unit and provider.
Does Extraplot predict future events?
No. It hides later observations from a historical series. A score compares your drawing with that known record and should not be treated as a forecast for future real-world values.