Reading the grid
Heavy black lines — the Sudoku boxes. Each one holds every digit exactly once, just like a row or column.
Thin dashed teal lines, set inside the cells — a cage. It never touches the bold Sudoku lines, so the two are never confused.
Solid gold outline — the cage your selected cell belongs to.
How points work
Signed in, solving a grid scores points — three things decide how many: base score set by the tier (100 Beginner up to 1000 Wizard), speed against the typical time for that tier, and how many hints you used. Your best score on each tier shows on Rankings and My Board.
Operations
+ the cage's digits add up to the target
− the largest digit minus the sum of the rest
× the cage's digits multiply to the target
÷ the largest digit divided by the product of the rest
? operation hidden — work it out from the digits that fit, then pick one