Number Sums presents a novel approach to numerical puzzle games by combining elements of Sudoku, KenKen, and arithmetic training into a single cohesive experience. Developed by Easybrain Ltd, the iOS application challenges users to solve grid-based puzzles where rows, columns, and colored regions must each sum to specific values indicated along the board's edges and within colored zones. The core mechanic involves selectively circling correct numbers while eliminating others to achieve simultaneous mathematical consistency across all constraints. The application features hundreds of progressively difficult puzzles organized into multiple difficulty tiers. Each puzzle requires players to apply combinatorial mathematics, logical deduction, and mental arithmetic skills. The interface provides number grids with color-coded regions, sum clues displayed along the periphery, and intuitive circle/erase controls. Advanced puzzles incorporate overlapping constraints that demand sophisticated pattern recognition and calculation strategies, effectively training multiple cognitive domains simultaneously. User experience benefits from clean visual design with distinct color coding, though some accessibility concerns emerge regarding font size in critical areas. The interface employs a minimalist approach with responsive touch controls, undo/redo functionality, and error checking features. Real-world usage patterns show players typically engage in short sessions of 5-15 minutes, with the puzzle structure lending itself well to both casual play and intensive problem-solving sessions. The absence of time pressure allows for methodical calculation, making it suitable for various engagement styles. User feedback indicates strong satisfaction with the core puzzle mechanics, though specific interface issues recur in reviews. Aging Eyes 2 (August 5, 2025) noted visibility challenges with small corner numbers, while ks5392 (July 6, 2025) suggested improved toggle visibility options. The developer demonstrates responsiveness to feedback, as evidenced by JeL Br's review (June 25, 2025) noting effective customer support interaction following initial technical issues. The 4.6-star rating reflects generally positive reception of the novel puzzle concept despite minor usability concerns. The application excels in providing intellectually stimulating content that genuinely enhances mental math capabilities, with puzzle variety ensuring long-term engagement. Limitations include occasional accessibility issues for users with visual impairments and some initial learning curve for understanding multi-constraint puzzles. Ideal for mathematics enthusiasts, puzzle lovers seeking beyond traditional Sudoku, and individuals interested in cognitive maintenance through numerical problem-solving activities. The game represents a valuable addition to the educational puzzle genre despite needing minor interface refinements.