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PRISM’s developer says he generated 240 light-routing puzzle levels by first building a solved board, scrambling it with reverse rotations, and then checking that each accepted level has exactly one solution. A separate breadth-first search checks that the displayed par—the intended minimum number of taps—is actually shortest. These checks describe the author’s implementation and reported catalog, not a universal guarantee about generated puzzles.
How PRISM’s light-routing puzzle works
In PRISM, tap a piece to rotate it 90 degrees, and the light immediately follows its new path. A board is solved when every crystal is lit simultaneously with exactly the color it requests. That rule gives the generator a concrete test: simulate the light, then determine whether the resulting board meets every crystal’s requirement.
Why generate a puzzle backwards?
Rather than start with an arbitrary board and hope it can be solved, the author’s generator starts with a solution. It lays out emitters and pieces, traces the light, and places a crystal matching the light color at each actual landing point. The result is solved by construction.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Next, it rotates pieces backwards by the chosen target number of taps. This scrambles the solved board; reversing those rotations provides a known path back to the solution. That establishes that the candidate has an intended solution, but it does not establish that no other solution exists.
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How the generator checks for exactly one solution
For each candidate, the author says the generator enumerates combinations of rotatable-piece orientations and counts how many produce a solved board. It keeps the candidate only if that count is exactly one. A count of zero means the board is unsolvable; a count above one means there are multiple solved states.
The count is abandoned and the candidate discarded if its state space exceeds 200,000, according to the author. That means the generator does not accept an over-limit candidate on the assumption that it is unique; it rejects it rather than claiming a completed uniqueness check.
This test also catches a less obvious problem: an irrelevant rotatable piece. If light never reaches a piece, changing its orientation may create additional solved states without changing the beam path. The board then fails the exactly-one-solution test.
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How the displayed par is checked
The target number of taps is selected before the board is scrambled, so it is the intended par, not a value inferred from appearance. The generator then runs breadth-first search from the scrambled state to find a shortest solution. If that shortest path differs from the target, the candidate is rejected.
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Because breadth-first search starts from the puzzle rather than relying only on the reverse rotations used to make it, it acts as an independent check on the claimed minimum. In the author’s account, it can reveal errors in the generator as well as confirm the par.
What else can disqualify a candidate?
Passing the solution and par checks is not enough for a level to make the catalog. The author lists additional quality gates:
- Reject boards that are too easy or already solved.
- Require enough crystals and reject boards where the light never bends.
- Check that a level demonstrates its chapter’s intended phenomenon, such as dispersion or color mixing.
Later chapters are harder to populate because they use more pieces and leave fewer useful empty cells; crystal placement also makes acceptable layouts less likely. The author reports that filling Chapter VI’s 45 levels took on the order of a million generation tries. The generator prints rejection counts for its gates, which helps tune chapter settings.
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A generator that runs correctly does not automatically prove that the level data ultimately shipped is correct. The author says checks run against the final data on every commit across all 240 levels. They test whether each level is solvable, whether applying the solver’s path clears the board, and whether exactly one solution exists.
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The author also recounts a bug exposed by the distinction between generation and final-data checks. After a rendering change made beam endpoints stop slightly short of absorbing pieces, the generator used an integer endpoint coordinate to decide whether light had reached a piece. Candidates containing walls were consequently rejected. The author says reachability was changed to use position and travel direction instead of endpoint coordinates. This is the developer’s account of the failure and fix.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.The reported 240-level catalog
The developer, 김종현, reported this six-chapter catalog and average par in 2026:
| Chapter | Levels | Average par |
|---|---|---|
| Reflection | 14 | 2.6 |
| Splitting | 32 | 3.7 |
| Dispersion | 44 | 5.1 |
| Mixing | 52 | 5.7 |
| Filtering | 53 | 7.2 |
| Convergence | 45 | 8.3 |
The totals and averages are the author’s reported results for PRISM, not independent benchmarks or evidence that the same pipeline will produce comparable results for another game. The author’s closing line captures the game’s intended attitude toward difficulty: “A level you cannot solve is not a bug, it is logic you have not seen yet.”
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