Keep Prime Numbers

Keep Prime Numbers is a single-player puzzle game developed by the independent studio Numeric Labs and released in 2023. The game is built entirely around the mathematical concept of prime numbers—positive integers greater than one that have no positive divisors other than one and themselves. The core objective requires the player to manipulate a grid of numbered tiles to isolate and preserve all prime values while eliminating composite numbers. The game presents a series of levels, each with a unique grid layout and a set of operations available to the player. The difficulty escalates as the grid size increases and the number of required moves decreases. The game does not feature a narrative or characters; its focus is purely on logical deduction and arithmetic reasoning. The visual design is minimalist, using a monochromatic color scheme with high-contrast numerals to reduce distraction. The soundtrack consists of ambient electronic tones that change pitch based on the primality of the numbers on screen. The game includes a level editor and a daily challenge mode that generates a new puzzle each day. Keep Prime Numbers is available on Windows, macOS, and Linux platforms.

The player controls the game using a mouse or touch input. The game board consists of a square grid, each cell containing a positive integer. The player selects a cell by clicking on it. Once selected, the player can perform one of two actions: swap the selected number with an adjacent number (up, down, left, or right) or remove the selected number from the grid. Removal is only permitted if the number is composite (non-prime). The goal is to remove all composite numbers from the grid, leaving only prime numbers in their original positions or after swaps. The player must complete the level within a specified number of moves, displayed in the upper-left corner of the screen. A move is counted for each swap or removal. The game provides a visual indicator: prime numbers are displayed in a distinct color (typically green), while composite numbers are shown in red. The player can undo the last move by pressing the Z key on the keyboard. The game does not have a pause function; the timer only runs during the daily challenge mode. The interface includes a reset button to restart the current level and a menu button to return to the level select screen. No tutorial is provided; the rules are explained through a single text screen at the start of the game.