Controls
On a phone, drag the slider or tap the step buttons. On a keyboard, focus the slider and use the arrow keys; Tab moves to the Lock In button, and Enter submits. The number next to the slider is your current estimate in metres.
How scoring works
An exact estimate earns 100 points. The score falls smoothly as your proportional error grows. Guessing twice the real size and guessing half the real size receive the same score. Every round uses the same rule:
Score = round(100 × e−1.2 × |log₂(estimate ÷ actual)|)
| Your estimate | Compared with actual | Score |
|---|---|---|
| Exact | 0% error | 100/100 |
| 1.1× actual | 10% too large | 85/100 |
| 1.25× actual | 25% too large | 68/100 |
| 1.5× actual | 50% too large | 50/100 |
| 2× actual | 100% too large | 30/100 |
What counts as the size?
The label under each object tells you what is measured. A lion’s shoulder height and an ostrich’s total height are different measurement types, even when both are shown against the same ground line. Read the object’s source record for its selected value and scope. Illustrations aid comparison but do not replace the written measurement.
Questions
Can I change an answer after Lock In?
No. You can see the source and move to the next round.
Do I have to use a mouse?
No. The slider, step buttons, and action buttons work with a keyboard.
Do practice rounds count toward the daily five?
No. Daily, unlimited, and animal sessions are separate.