Center of Mass

Points stream onto a horizontal axis in real time. The mean is drawn as a glowing balance triangle that swings whenever an outlier lands, while the median holds steady nearby. Drag your marker to track the moving mean as closely as you can. The longer you stay on it, the more you score, over a 60-second round.

• Outliers drag the mean hard but barely move the median.
• Accuracy is rewarded continuously, so anticipate the lurch.
• The round ends after the timer; a summary contrasts mean versus median.

• Desktop: press and drag anywhere on the axis to move your marker.
• Phone & tablet: drag with your finger, fully touch-friendly.

• Calm, Normal and Storm difficulty (more frequent, more extreme outliers), each in Daily or Practice.

• When a far-out point lands, nudge toward it immediately, the mean will chase it.
• Don't over-react to clusters near the middle; the mean moves less there.

Center of Mass is a real-time tracking game that makes the difference between mean and median tangible.

• Skills: mean and median, measures of center, distributions
• Best for: roughly grades 7–12 (ages 12+)
• For parents & teachers: mean versus median, made physical.

Drawing the mean as a balance point that swings when an outlier lands is literally what the mean is: the value about which the deviations sum to zero.

Showing the median alongside it, unmoved, is the original comparison.

That contrast is the whole case for robust statistics. One extreme value drags the mean as far as you like and moves the median by at most one position, which is why the choice between them is a decision about how much a single observation should be allowed to say.

Center of Mass is a real-time tracking game that makes the difference between mean and median tangible. It's an original free browser game made for PlayPendium.

A free, original browser game on PlayPendium. No download, no install.