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Lizely

Number Balance

Choose the missing one-digit weight that makes both sides of five number scales equal.

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How to use

  1. 1.Add every known block on the left pan, then add the known blocks on the right pan.
  2. 2.Press a digit from 1 through 9 that makes the right total equal the left total.
  3. 3.Balance all five scales with the clean key 4, 3, 4, 4, 8 before making two mistakes.

About Number Balance

Number Balance is a five-round missing-weight game built around equality. Each round shows known number blocks on the left pan and known blocks plus a question-mark block on the right. Choose one digit from 1 through 9 so the two sums become exactly equal.

The challenge is a disclosed Lizely product fixture rather than an external table or standardized assessment. Its five equations, accepted answer range, two-strike rule, score, and order are fixed in the page and pure logic test. Every answer follows directly from elementary addition and can be checked from the visible blocks.

Round one places 2 and 3 on the left against 1 plus the unknown on the right. The left total is 5, so the missing weight is 4. Round two places 7 against 2 + 2 + ?, making 3 the only balancing digit. Round three places 1 + 4 + 2 against 3 + ?, so the answer is 4.

Round four shows 9 + 1 against 6 + ?, which again needs 4. Round five shows 3 + 3 + 3 against 1 + ?, so the missing weight is 8. The clean keyboard route is therefore 4, 3, 4, 4, 8. Five correct rounds award 200 points each and finish at 1,000.

Press a number key from 1 through 9 to answer immediately. Mouse and touch users can press the same nine visible buttons. The game intentionally excludes zero and multi-digit answers because every disclosed fixture has exactly one valid single-digit solution. Invalid keys and out-of-range logic calls leave the state unchanged.

A correct digit advances to the next scale. A wrong digit leaves the same scale visible and increments the mistake counter. One mistake is recoverable, allowing the player to recalculate both sides. A second mistake creates a terminal deadlock; further answers are ignored until Restart. This provides an observable failure path without a hidden timer or arbitrary speed penalty.

The logic separates the displayed fixture from its validation. getBalanceTotals independently sums all fixed left blocks, all fixed right blocks, and the proposed missing weight. answerBalance compares the selected digit with the fixture's disclosed answer, advances only on equality, and freezes completed or deadlocked states.

The isolated test asserts all five disclosed answers, recomputes both totals for every winning digit, proves a neighboring digit does not balance each scale, simulates the complete five-key 1,000-point run, reaches the two-error deadlock, proves terminal-state freezing, and rejects zero and ten. Expected totals are explicit product goldens rather than values copied from the UI.

The visual scale uses semantic HTML and CSS borders, flex layout, and site color variables; it does not use canvas or hardcoded colors. Each pan and choice is keyboard-accessible and remains readable on a narrow screen. There is no random generator, animation dependency, account, network call, audio, download, hardware permission, or pointer precision requirement.

Restart returns to the first 2 + 3 scale with zero points and zero mistakes. A completed best score remains only in the current browser's localStorage. Double-press Escape to show the simulated spreadsheet boss screen, then repeat it to resume the unchanged scale. For more arithmetic breaks, try Addition Maze, Math Crossword, Number Sequence Quiz, or Number Match 10.

Methodology & sources

Five immutable fixtures store left weights, known right weights, and one answer from 1 through 9. getBalanceTotals sums each pan with a proposed digit. A correct digit advances and adds 200; a wrong digit increments mistakes; two mistakes deadlock; five correct answers complete at 1,000. Terminal and out-of-range inputs are ignored.

Frequently asked questions

Why can the answer 4 appear in several rounds?
Each scale is independent. Values do not need to be unique across the five fixed equations.
What happens after one wrong weight?
The same scale stays visible and the mistake counter becomes one, so you can recalculate.
Can the missing weight be zero or greater than nine?
No. Every fixture has one disclosed solution in the 1-through-9 button range.
How is the score calculated?
Each balanced scale adds 200 points. Five correct scales produce the maximum 1,000.

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