FA-86664 / Procedural level generation constraints / Member archive

Wall autotile bitmask: North bit samples the south neighbour · case 04

Wall tops render as if the wall continued below.

Member previewVariant 4 · 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
vertical wall pair #1	`[[5], [0]]`	`[[4], [1]]`	Failed

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