Rules & quick reference
| Start | 1 nonzero digit |
|---|---|
| Exposure | 1 + 0.5 × digit count seconds, capped at 12 seconds |
| Comparison | Exact digit string; no numerical rounding |
| Maximum | 30 digits; first incorrect answer ends the run |
Recall the complete string
Start a level to reveal a random number. Watch the time bar: the input appears only after the memorization interval ends. Type the full string in the original order and select Check answer or press Enter. A correct response unlocks a longer string. The first digit is never zero, but a later digit can be zero and repeated digits are allowed. A wrong answer ends the run and shows the original string for comparison.
Why the answer stays a string
Long digit sequences can exceed the integer precision available to JavaScript numbers. This tool generates and compares character strings, avoiding rounding in long answers. The score is the longest digit count completed, with zero recorded if the one-digit level is missed. Exposure grows by half a second per digit after the initial one-second allowance and stops growing at twelve seconds. A complete thirty-digit recall finishes the maximum level.
Chunking changes what a digit count means
A familiar date or repeated pattern may be remembered as a unit rather than as independent digits. That is one reason a digit count cannot be treated as a direct count of abstract memory slots. The commonly quoted seven-plus-or-minus-two observation is historical context, not an individual pass mark for this game. Different experiments control presentation, rehearsal and chunking in different ways. This site does not derive an age, IQ or medical conclusion from your result.
Keep rehearsal conditions consistent
Decide whether you will rehearse silently, say the digits aloud or use a grouping strategy, then keep that method consistent across runs. A larger font can help readability but does not standardize the physical viewing distance. Reading a string and entering it with a keyboard are separate parts of the task; a typo can end a run even when you remember the digits. Use repeated sessions to explore your strategy, and treat the score as practice feedback rather than a durable personal label.
Your result stays on this device
Completed game results are saved in this browser when local storage is available. Bests and recent history describe this device’s saved runs, not a public leaderboard. Changing browsers, clearing site data or using private browsing can remove them. Copy score writes only the visible result summary to your clipboard when you request it; sharing is your choice. Clear local game data removes scores, daily completion markers and the saved 2048 board for this origin. No game result is uploaded, and the games remain usable when persistent storage is unavailable. Use the rule table to check what the active mode measures before comparing another session. A changed duration, input method or grid difficulty can change the task even when the displayed score uses the same unit.
Frequently asked questions
Are long answers rounded?
No. Both the target and the submitted answer are compared as digit strings.
Does seven digits mean average memory?
No. Historical memory-span observations are not a norm for this implementation.
Does the number stay visible while I type?
No. The input opens after the string disappears.
What ends the run?
The first incorrect answer, or successful completion of the 30-digit level.
Built by Mihai · Reviewed 2026-10-24 · Read the related technical guide · Testing policy