About Coin Weighing
Choose equal groups for a two-pan balance and use the evidence to identify one heavier coin. The scale keeps the largest possible suspect group, so a good comparison must work whichever result survives.
Explore 59 cases with different coin counts and pan capacities. Genuine coins remain useful as counterweights. Finish with fewer weighings, or set a faster first-solve time.
How to play
- Goal
- Find the one heavier coin using equal groups on a balance. The scale keeps the largest possible suspect group, rather than choosing a random hidden coin. Ties prefer balance, then left heavy, then right heavy.
- How it ends
- Evidence must leave one suspect, then Identify seals the case. There is no loss limit.
- Record
- Fastest first solve and fewest weighings are separate records.
- Choose a case to reveal its coins and start the first clock. Exactly one coin is heavier; every other coin has the same weight.
- Select a numbered coin, then Left pan, Right pan or Table. Load the same positive number on both pans, within the stated capacity.
- Press Weigh. The scale keeps the largest suspect group consistent with the evidence. Equal-size ties prefer balance, then left heavy, then right heavy. A comparison that cannot remove any suspect is unavailable.
- A tilt keeps suspects on the heavier pan. Balance keeps suspects left on the table. Pale genuine coins can still be used as counterweights. The notebook records each comparison.
- When one suspect remains, press Identify to complete the case. There is no losing limit and no Undo for committed comparisons.
- Restart clears the current evidence after confirmation, keeps every spent weighing and makes the attempt practice. Replay can improve fewest weighings; only the first completed time is kept.
Controls
| Input | Action |
|---|---|
| Tap / click a coin, then a destination | Choose a coin and assign it to a pan or table |
| Arrow keys / Enter | Focus and select a coin or button |
| L / R / T | Assign the selected coin left / right / table |
| W | Weigh |
| Shift+R | Request Restart |
| Escape | Close a panel or return to Cases |
| Gamepad D-pad / A | Focus and activate |
| Gamepad LB / RB | Cycle the selected coin’s destination |
| Gamepad B / Start / Back | Go back / open the menu / open the rules |
Tips
- Plan for every result Split the suspects so even the largest remaining group is small. The scale will keep that group.
- Keep genuine counterweights A coin ruled out as heavy can balance a suspect on the other pan. This can distinguish two suspects without weighing them against each other.
Good to know
Progress saves in this browser when storage is available. The first clock continues through menus and chooser visits. Reload restores evidence but makes its time practice. A case open in another tab may be local-only. More than 256 recorded actions stays local-only; very long histories may stop saving. Music, effects and reduced motion have separate settings.
Watch how to play
Questions
Is the heavy coin chosen randomly?
No. Each result preserves the largest group still consistent with the evidence. The complete tie order is stated in the rules.
Must the heavy coin be on a pan?
No. If the pans balance, it is among the suspects left on the table.
Can I guess the coin?
No. Identify becomes available only when the evidence leaves exactly one suspect.
Can Restart erase spent weighings?
No. Restart clears the current evidence and placements while retaining every spent comparison. Its time becomes practice.
