You're dealt a handful of numbers and a target, wire them together with the four operations until the maths lands exactly on the goal.
Build an expression that uses every dealt number exactly once and evaluates to the target. Drop a number into the row, add an operator, and use parentheses as walls you draw so the order of operations becomes visible structure. The running value updates live and honours precedence, so you can see how close you are. Hit the target with all numbers used to solve.
Operator makes order of operations something you control, by drawing the parentheses yourself, you see exactly how grouping changes a calculation's result.
Using every dealt number exactly once to hit a target is the 24 puzzle, played as a card game in Shanghai since the 1960s: manipulate four integers so the result is 24, with all four used once.
The original element is that parentheses are walls you draw, so the order of operations becomes visible structure rather than a convention you carry in your head.
That makes the game about the thing people actually get wrong. Precedence is a ranking, not a law of arithmetic — calculators and programming languages do not all agree on it — and drawing the brackets turns an invisible ranking into something you can see and move.
Operator is an original, free browser number-combination puzzle that makes order of operations tangible by letting you draw the parentheses yourself. No sign-up needed.