Isobath guide — how to play, the distance tiers, and the FAQ
Isobath asks you to do something a quiz cannot: not name a place, but point at it. Here is how a day works, what the distances mean, and how to get better at it.
How a round works
- Read the city. One name appears over the water — say, Valparaíso. That is all the information you get.
- Tap the chart. A pin drops where you tapped. Nothing is committed yet.
- Adjust it. Drag the pin and it follows your finger exactly. Pinch to zoom in for a closer look — the pin stays on its coordinate while the chart moves under it, so zooming never nudges your answer. Double-tap cycles through the three zoom levels.
- Confirm. Only then does the round lock. A stray tap can never cost you a round, and you can re-place the pin as often as you like before confirming.
- Watch the reveal. The true location is struck onto the chart, the error arc is cast along the great circle between the two, and the distance counts up to its final value.
- Repeat five times, then see your total, where it falls against the shipped benchmark curve, and your streak.
On a computer, click instead of tapping. The chart is also fully keyboard-operable: Enter drops a pin at the centre, the arrow keys nudge it half a degree at a time (hold Shift for a tenth of a degree), and + and − step through the zoom levels.
Questions and answers
How do you play Isobath?
Five cities, one at a time, on a blank world map. Tap to drop a pin, drag to adjust, tap Confirm. The map reveals the true location with an arc and a distance in kilometres. Five rounds, about two minutes.
What does “off by 412 km” mean?
The great-circle (shortest-path-over-the-globe) distance between your pin and the city’s real coordinates, in kilometres.
What are the distance tiers?
A guess falls into one of five bands, by how far off it was: under 25 km is a pinpoint, under 150 km is close, under 600 km is the right region, under 2,000 km is the wrong region, and 2,000 km or more is a continent off.
| Under 25 km | Pinpoint |
| 25–150 km | Close |
| 150–600 km | Right region |
| 600–2 000 km | Wrong region |
| 2 000 km or more | A continent off |
What does “better than 68% of our benchmark” mean?
Your total compared against a fixed benchmark curve that ships with the game and is computed in your own browser. It is not a live comparison with other people: no server of ours ever receives your score, so we cannot know what anyone else scored, and we do not pretend to. The curve is a reference spread of plausible five-round totals, not a record of real attempts.
Does Isobath use Street View or satellite images?
No. The map is drawn from public-domain Natural Earth coastline data, rendered by the game itself. There is no Street View, no satellite imagery, and no third-party map tiles.
Why does the map have no country borders or names?
Isobath shows coastlines only. Borders and labels would give the answer away, and it keeps the game out of territorial disputes.
Will it work on my school or office network?
Usually, yes. Isobath loads no imagery and calls no map service, so it works where Street-View- and tile-based games are blocked.
How does the streak work?
One puzzle per UTC day; playing the day’s puzzle extends the streak, missing a UTC day resets it. It is stored in your browser only.
Can I play past days?
Past puzzles and their answer maps are published at /day/YYYY-MM-DD; the archive is at /day/. Your score is only recorded for the live day.
How are the cities chosen?
From a fixed, curated pool, seeded by the UTC date, so everyone worldwide gets the same five. They are graded so the rounds get harder.
Is it free, and do I need an account?
Free, no account, no install. Ads support it and consent is handled through Google’s consent tool. No score or location data is uploaded.
Tips that actually move a score
- Find the coastline first. Almost every city in the pool is near water, and a coastline is the only landmark the chart gives you. Place the coast, then walk inland.
- Use latitude before longitude. Most people know roughly how far north or south somewhere is — hot, cold, temperate — and that single band cuts the map to a strip.
- Zoom before you commit, not after. At the default zoom a thumb covers several hundred kilometres. One zoom level turns a “wrong region” into a “close”.
- Anchor on a city you are sure of. If you know where Lima is, you can reason about anywhere else on that coast relative to it.
- Remember the shape of a country, not its name. The chart will never label anything, so the silhouette of the Bay of Bengal or the Gulf of Guinea is worth more here than a list of capitals.
- Expect the difficulty to climb. Round one is usually a city most people could place; round five is not. Spend your care at the end.
About the map
Every coastline here is drawn from the Natural Earth 1:110m vector dataset, which is in the public domain. The chart shows physical shorelines and nothing else. It carries no political borders, no country or regional outlines and no flags, and none can be added — the geometry simply is not in the game.
Places whose sovereignty is actively disputed are deliberately left out of the city pool. Isobath takes no position on any territorial question, and the presence or absence of any place on the chart is not a statement about its status. Omitting a contested place is the only honest option for a game that draws no boundaries: naming one would mean taking a side we have no business taking.
The chart is also simplified for play. At 1:110m the coastline is generalised, small islands are dropped and the projection flattens as you move away from the equator. It is a game board, not a map: it is not suitable for navigation or for measuring anything in the real world.
About the distances
Each distance is the great-circle distance between your pin and the city’s stored coordinate, computed in your browser on that same simplified dataset. It is an estimate shown for entertainment only. Coastal generalisation, rounded city coordinates and the chart’s projection all mean the figure will differ by some kilometres from a surveyed value, so it must not be relied on for navigation or for any real-world decision.
Still stuck?
If a city is misplaced or the chart misbehaves, write to auto-ai-agency@quantum-solutions.hr.