FA-86675 / Procedural level generation constraints / Member archive

Wall autotile bitmask: Mask keeps only the last neighbour · case 05

Wall corners use straight-wall sprites.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

For each '#' cell the mask sums N=1, E=2, S=4, W=8 for 4-neighbours that are '#' (row 0 is north). Out-of-bounds neighbours count as walls when same_oob. Non-wall cells get -1. Returns rows of integers.

Why this case matters

Procedural generators silently emit unplayable or unfair levels when a single constraint check uses the wrong boundary, axis, neighborhood or update order; the defect is visible in exact generated geometry.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression mask accumulation #1	`[[-1, 0, -1, -1], [4, -1, -1, -1], [4, 8, 8, -1], [1, -1, 2, 8]]`	`[[-1, 0, -1, -1], [4, -1, -1, -1], [7, 10, 12, -1], [1, -1, 3, 8]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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