The Scale
A daily balancing challenge: you split 8 countries between the two pans of a scale so the totals end up as even as possible.
How to play
Some days you weigh population and other days area: population on Mondays, Wednesdays, Fridays and Sundays, area on Tuesdays, Thursdays and Saturdays, by the UTC date. Drag each country onto a pan, or tap it and then tap the pan. Any split is allowed, even 7 against 1.
Before confirming you can weigh up to 3 times: the scale tips towards the heavier side but shows no numbers. When you're sure, tap Confirm. You get one attempt per day.
Scoring
Your difference is measured as a percentage of the total. You get 3 stars if you match the best possible split, 2 if you are within 3% and 1 if you are within 10%. Two stars or more is a win. Hit the perfect balance without using a single weighing and you also get the By eye badge. At the end you see what the best split was.
How each day is built
The 8 countries are the same for everyone and change at midnight UTC. They always come from at least three continents, none of them is more than 45% of the total, and there is always a split with a difference of 1.5% or less, so a near-perfect balance is always possible.
Tips
Start with the heaviest country and build the other pan around it: one giant can weigh as much as five small countries. Use the weighings on countries you don't know well, not on the ones you're sure of. And keep the lightest countries for last, because they are what you fine-tune with. A weighing that comes out nearly level tells you more than one that tips hard: it means moving one small country is enough.
What you learn
To compare countries in proportion, not just in order. To balance the scale you need a rough idea of how many times one fits into another, and that leaves you with a much sharper sense of population and area figures.