Eyeballing Line of Best Fit Game
Best Fit Blitz is a free browser game about estimating a line of best fit by eye. Each round presents an original synthetic scatterplot and a movable coral line. Drag the two large handles until the line seems to balance the cloud of points, then submit your answer. The ordinary least-squares benchmark, vertical residuals, and score remain hidden until the choice is locked, so the task tests visual judgment instead of tracing a displayed solution.
How to play the five-round challenge
Begin by looking at the broad direction of the points rather than any one dot. Move the left and right handles to change both the height and slope of your line. Pointer users can drag either handle. Keyboard users can focus the graph, press Space to switch the selected handle, and use the arrow keys for small adjustments. Holding Shift makes each keyboard step larger. Submit only when the line feels centered within the scatter. After the answer appears, select Next Round and repeat until all five rounds are complete.
The controls are designed for a phone as well as a desktop. Touch handles are deliberately large, the game uses no hover-only action, and the graph scales to a 390-pixel viewport without losing the full play loop. New Seed creates another repeatable set of five scatterplots. No account, installation, worksheet, or calculation is required before play.
How the line of best fit score works
For each synthetic dataset, the game calculates the ordinary least-squares line after you submit. That benchmark is the straight line with the smallest possible sum of squared vertical residuals for those points. Your line has its own sum of squared residuals. Best Fit Blitz subtracts the benchmark error from your error to isolate avoidable excess error, then divides that value by the total variation in y, also called SST. This normalized excess SSE is mapped to a score from zero to 100. Matching the benchmark earns 100, while increasingly avoidable error lowers the score.
Normalizing by SST makes the feedback comparable across rounds whose dots have different amounts of vertical spread. A small numerical safeguard handles datasets with almost no y variation, so the score remains finite. The result is practice feedback for this game, not a school grade, formal assessment, or statistical certification.
Why the benchmark is hidden before submission
Eyeballing a trend is a different skill from following a line that is already visible. Before submission, the game shows only the points and your chosen line. It does not reveal the benchmark slope, intercept, residuals, SSE, or score. After submission, the dashed mint line identifies the ordinary least-squares solution and pale vertical marks show the benchmark residuals. This order makes the comparison useful: first commit to a visual estimate, then inspect exactly where the two lines differ.
What to notice in a scatterplot
Try to balance the size and number of gaps above and below the line. Avoid connecting the first and last points automatically, because extreme dots can pull the eye away from the center of the cloud. Check whether the line follows the overall direction across the full x range. A strong estimate usually passes through the middle of the pattern while leaving no large systematic band of positive residuals on one side and negative residuals on the other.
Original data and clean-room implementation
Every round is generated locally from an original deterministic data generator. A visible URL seed can reproduce a set for debugging, while New Seed selects another run. The site does not copy a textbook chart, worksheet prompt, competitor question bank, scoring rule, source code, or visual trade dress. The mathematical ideas of linear regression, residuals, SSE, and SST are implemented independently from standard definitions. The About page explains the project's scope and the full instructions provide an accessible rules reference.
Questions about Best Fit Blitz
Do I need to calculate a regression equation?
No. The game asks for an estimate by eye. It performs the benchmark calculation after submission so you can compare intuition with the least-squares result.
Does the site collect my answers?
Only players who select Allow enable consent-gated Google Analytics 4. No advertising or account system is connected, and scores and handle positions stay in the current page session. Read the Privacy Policy for details and withdrawal controls.
Can I use this as a graded assessment?
The game is casual educational practice. Teachers may use it as a discussion prompt, but its score is not designed as a validated assessment. The Terms of Service describe this limitation. Technical questions can be sent through the public route listed on the Contact page.