TERRAXIS

What is TERRAXIS

TERRAXIS gives you a square grid and a handful of real countries. Each row carries its own ordering rule — area, population, latitude, longitude, land neighbours or the length of the English name — and every column shares one further rule. You tap a country in the pool, place it in a cell, and rearrange until each row rises from left to right and each column rises from top to bottom.

The difficulty is not knowing the figures. It is that every country has to satisfy two rules at once: its row rule and the shared column rule. A country that sits perfectly by area may be hopeless by latitude, so a single correction ripples across the grid. Because the rules come from unrelated properties of the world, your intuitions disagree with each other. Australia is enormous and nearly empty, Israel is tiny and crowded. You end up holding several rankings of the same countries in your head at once.

How to play

1. Pick a level, from Cadet 3×3 to Meridian 6×6, then read the labels. The chip above the grid gives the column rule, shared by every column; the chip beside each row gives that row's rule.
2. Tap a country in the pool, then tap a cell to place it. Tap a placed country to select it: tap it again to send it back to the pool, or tap another cell to swap the two countries.
3. Press Check whenever you like. It tests only what you have already placed and turns any out-of-order line red. Each check costs 40 points.
4. Fill the grid so that every row and every column is in order. The round ends the moment the last piece lands correctly, and your score, time and number of checks go into the ranking.

Strategies that work

• Solve the columns before the rows. Sort the whole pool by the column rule, cut that sorted list into equal blocks, and give the smallest block to the top row, the next to the second row, and so on. The columns are then correct whatever the order inside a row, and you only have to sort each row by its own rule.
• Latitude and longitude come from each country's capital, not from the middle of its territory. Russia enters by Moscow, the United States by Washington. On a longitude axis that matters: Russia lands near Europe rather than deep in Asia.
• Name length counts the English name whatever your interface language, and only the letters count. United States is thirteen, DR Congo is seven, South Africa is twelve.
• The rules are not equally kind. Area separates countries by orders of magnitude and is easy to rank by eye; population is far tighter in the middle of the table. Land neighbours is the trap: every island is zero, so Japan, Iceland, Cuba, Madagascar and Australia all belong at the low end of that axis.
• Weigh each check against the clock. A check always costs 40 points, while the time bonus is two points per second saved, multiplied by the level. On a 3×3 board that is about twenty seconds of bonus; on the 6×6 board it is under five. Check freely on big grids, rarely on small ones.

A little history

TERRAXIS is an original puzzle built for puzzle-me.com. It has no older history and no inventor to name, but the two ideas behind it are well established. The first is the ordering constraint: grids whose rows and columns must respect an inequality. That family includes Futoshiki, the Latin square variant driven by greater-than signs between cells, and it goes back to the study of Latin squares themselves, which Leonhard Euler worked on in the eighteenth century. The second idea is the statistical almanac. Ranking countries by area, population and position is what geographical tables have done since atlases began printing figures beside their maps.

Frequently asked questions