Troubleshooting and FAQ

A decoder or restorer returned null

decodeLayout rejects invalid dimensions, unknown pipe characters, missing sources and invalid source/drain placements. newGame inherits that validation. gameFromProgress also checks the progress belongs to that board; gameFromCode rejects changes to shapes, locked pieces, endpoints or block integrity. Keep the original code with saved progress. levelSolution and levelAnswer return null when a row's code or turn digits cannot be read.

A metadata call returned null

Unknown levels have no size, score, marks or piece count. A level may legitimately have no teaching/testing role. firstUnsolvedLevel returning null means completion of the supplied set. hintFor returning null means no answer-facing piece remains to correct. quartersBetween, tapsBetween and blockQuartersBetween return null for incompatible shapes or turns. An unknown guide/shape identifier returns undefined, not null.

Loading and search questions

A supported size must load before suidoLevelsOf, and the big collection before suidoBigLevelsLoaded; otherwise they throw. Invalid daily dates throw rather than rolling into the next month. For an inconclusive solver budget, inspect complete and increase the budget deliberately; never interpret one found answer as a proof.

A mount returning null needs a valid board and compatible answer/progress. If the board is only an image, use /play for controls. grid and display size have different jobs; see embeds and the full contract.