What is Headcount?
Headcount shows Earth at night with population hotspots glowing where people live. You draw a single loop around any area to capture an exact target number of inhabitants. The official trace is blind—no running counter—and scoring follows a ratio curve where 100 is perfect, half the target scores the same as double, and small deviations cost less than large ones. Population data comes from the European Commission Joint Research Centre's GHS-POP dataset.
How to play Headcount
Read the target population above the map. In Pan mode, zoom and position the view over the region you want to encircle. Switch to Draw mode and trace a loop around the bright areas in any shape. Before submitting, drag the loop from inside it to reposition it.
Submit once for the official daily attempt. The total population remains hidden while you draw. For new targets, switch to Practice mode; the enclosed population is shown after each submission.
Reading the scoring curve
The score is based on the ratio between your loop’s population and the target. An exact match earns 100. Proportional errors are treated symmetrically: enclosing half the target or twice the target gives a score of 69.9. A loop covering 9.4 million people against a 10 million target scores 97.3, and a 2% miss still scores above 98. In an official attempt, population counts remain hidden until you submit. Practice mode shows the actual count inside each loop.
Why the map matters
Brightness represents population. A compact city cluster and a long coastal strip can contain the same number of people, so the glow’s intensity is the only reliable guide. The night view is the puzzle. Reading its hotspots determines whether your loop comes close to the target or misses by a factor of two.
Tips for a tighter loop
Set your view in Pan mode before switching to Draw. The official trace is blind, so your chosen zoom level is the only reference you have.
Encircling an entire urban area is often safer than trying to cut through the middle of a larger one. The ratio curve penalizes undershooting as much as overshooting, so aiming slightly wide can be less costly than missing small.
Use Practice as calibration. It reveals the population inside each loop, letting you measure whether your eye consistently aims too high or too low.
Modes
Daily Game
One numbered and dated target, one loop, one official submission with no live feedback.
Practice
Unlocked after the daily attempt. Generates fresh targets each round and displays the population count for every submitted loop.