Game Guide
Balance Scale is subtraction wearing a physical costume. Here are the five free levels, the counting up method, and how to read the beam when you are wrong.
Balance Scale is the simplest game in the MyRin catalogue to describe and one of the more quietly useful ones. A beam, two pans. The left pan holds a known total. The right pan holds a known weight plus a gap, and you choose the weight that fills the gap so the beam sits level.
That is one subtraction per level, and if you only wanted the arithmetic you would not need the scale. What the scale adds is a meaning for the equals sign: balanced, not "the answer goes here". It is worth playing for that reason alone, and it is why this game reads so well for younger players.
Here is the MyRin short for Balance Scale. The tilt animation is the part that does not survive a screenshot, so the clip is the better introduction.
Left total minus the fixed right weight equals the missing weight. Every level is that, and the only thing that changes is the size of the numbers.
The method worth using, though, is not subtraction. It is counting up. Instead of asking "what is 85 minus 58?", ask "58 plus what makes 85?" Most people compute the second faster and with fewer errors, because moving forward through the number line is easier than moving backward, and because it lets you take the journey in convenient steps: 58 to 60 is 2, 60 to 85 is 25, so the answer is 27.
Counting up in steps also matches what the scale is showing you. You are adding weight to the right pan until it reaches the left, which is literally what the arithmetic is doing.
Choices 3, 5, 7, 9. Counting up: 7 to 12 is 5. The answer is 5.
Small enough to be recall rather than calculation, which makes it the right place to watch what the beam does when you are right: it settles level, with no tilt. Establishing what correct looks like is worth one level.
Choices 10, 12, 14, 16. Counting up: 18 to 20 is 2, 20 to 30 is 10, total 12.
Two steps through a round number, which is the pattern for every remaining level. Notice that the choices are spaced two apart, so a rough estimate does not get you there. You have to be exact, and the game is quietly training exactness by choosing its distractors this way.
Choices 15, 18, 20, 25. Both numbers are round, so 60 minus 40 is 20 directly, no stepping needed.
An easy level positioned between two harder ones, and worth using deliberately: try it once by counting up and once by subtracting, and notice which felt faster for you. People differ here, and knowing your own preference is worth more than following advice about it.
Choices 22, 24, 27, 30. This is the hardest level in the demo. Counting up: 58 to 60 is 2, 60 to 85 is 25, total 27.
Try the alternative and see the cost: 85 minus 58 by subtraction requires a borrow, and borrowing is where mental arithmetic errors concentrate. Counting up avoided the borrow entirely by going through 60. That is the whole argument for the method in one example.
The distractors are also instructive. 24 and 30 are the answers you get from plausible slips, over or undershooting the round number step, and they are there on purpose.
Choices 30, 33, 35, 40. The answer is 35, and if it took you any time at all, the fix is a memorisation job rather than a method one.
Complements to 100 are the most reusable set of arithmetic facts there is, and there are only a handful worth installing: 65 with 35, 63 with 37, 45 with 55, 28 with 72, 82 with 18. Subtracting from 100 turns up constantly in shopping, percentages and timekeeping, and it is the one place where flat recall genuinely beats any clever method. Arithmetic Blitz leans on the same complements, but under a seven second clock.
The beam does not just say right or wrong. It tilts in proportion to how far off you were and in the direction of the heavier pan, capped so the animation stays readable rather than flipping off screen.
That makes it diagnostic. A beam that dips slightly toward the left means your weight was a little too small. A steep dip means you were badly off, probably by a full step in the wrong direction. A dip toward the right means you overshot. Reading the tilt before reading the verdict is a better habit than the reverse, because the tilt tells you what kind of error you made, and the verdict only tells you that you made one.
This is also the part of the game that carries an idea worth having. In an equation, both sides are the same quantity described differently, and a wrong answer is not a failed lookup but an imbalance with a size and a direction. Learners who read the equals sign as an instruction to produce an answer struggle later with algebra in a way that learners who read it as a statement of sameness do not. A tilting beam teaches the second reading without saying a word about it.
Mental subtraction fluency, primarily, and specifically the counting up strategy, which transfers directly to working out change, durations and differences in everyday numbers. Secondarily, and more interestingly, it builds an intuition for equality as balance.
The arithmetic ceiling in the demo is low: nothing here exceeds two digit subtraction. That makes the five levels suitable for a much wider age range than the numbers suggest, and it means an adult will finish them in under two minutes. The installed game extends the same mechanic across 600 levels with larger numbers and, at the harder difficulties, more than one unknown weight on the beam, which is where it starts being genuinely algebraic.