Parity Planning
Switch every light off
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What is the Parity Planning?
Lights Out is a grid puzzle in which every light you press toggles itself and the lights directly above, below, left and right of it. The goal is to switch the whole grid off. It became widely known as a handheld electronic game in the 1990s, and it has since become a favourite example in recreational mathematics, because every solvable board can be analysed with simple arithmetic on odd and even numbers.
Parity Planning is the Neuroptimize take on Lights Out. Each board shows a par, the fewest taps that can solve it, and your task is to clear the grid within a couple of taps of that number. Because pressing a light twice undoes itself, success depends on choosing which lights to press, not the order. The grids grow from 3 by 3 to 5 by 5 as you level up.
How to play the Parity Planning
- A grid of lights appears with some of them switched on. Tapping any light flips it and its direct neighbours (up, down, left and right) between on and off.
- Switch every light off to solve the board. The pills above the grid show the par (the minimum number of taps needed), your tap count and how many lights are still lit.
- A board counts as solved if you clear it within par plus 2 taps. Hitting par exactly is a perfect solve and earns bonus points.
- Reset restores the starting pattern, but taps you have already made still count. If you go more than 2 taps over par, a Skip board button appears, and skipping counts as a miss.
- A session is 6 boards or 90 seconds, whichever comes first.
- Levels 1 to 8 use a 3 by 3 grid, levels 9 to 18 use 4 by 4, and level 19 and above use 5 by 5. Within each size the par rises, so boards need more taps to clear.
Strategies and tips
Never tap the same light twice
Two presses on one light cancel out exactly. A perfect solution never presses any light more than once, so if you catch yourself going back to a light, you are wasting taps.
Order does not matter
The final board depends only on which lights you pressed, not the sequence. This means you can plan the full set of taps before starting and press them in any order you like.
Chase the lights downwards
A reliable method is light chasing: for each lit light in a row, press the light directly below it. Work down the grid row by row until only the bottom row may be lit. It will not always hit par, but it shows you which top-row presses are needed.
Look for plus shapes
A single press makes a plus-shaped pattern, or a smaller T or corner shape at the edges. If you see one of these patterns lit on its own, one tap in its centre clears it.
Use the par as a clue
The par tells you exactly how many presses the best solution uses. On a small board, if par is 2, look for two plus shapes that overlap to make the lit pattern. Presses that overlap cancel shared cells.
Mind the clock on big boards
Six boards must fit into 90 seconds, and 5 by 5 boards take longer to read. Plan quickly, and if a board goes badly, a reset is usually faster than trying to repair it tap by tap.
The science behind the Parity Planning
Lights Out is a puzzle in which pressing a light toggles it and its neighbours, with the goal of switching every light off. Because pressing a light twice cancels the first press, a solution depends only on whether each light is pressed an odd or even number of times. Solving it efficiently requires planning moves in advance rather than trial and error.
Frequently asked questions
Is every Lights Out puzzle solvable?
Not every possible pattern can be solved on every grid size. The boards in Parity Planning are always built by pressing lights on an empty grid, so every board has a solution and the game knows its exact minimum number of taps.
What is the trick to solving Lights Out?
Remember that pressing a light twice cancels out and that order does not matter. A common method is light chasing: press the light below each lit light, row by row, then adjust the top row based on what is left at the bottom.
Why is it called Parity Planning?
Parity means whether a number is odd or even. In Lights Out, only the parity of presses on each light matters, so solving it is really about planning which lights get an odd number of presses.
Is Parity Planning free?
Parity Planning is a Pro game in Neuroptimize, and Pro starts with a 7-day free trial. Free players can also get it as the Pro game of the day in their daily workout.