FAILURE MAP
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FA-86436 / Procedural level generation constraints / Open access

Enemy spawn point selection: Spawns may touch each other · case 01

Enemy packs spawn stacked on adjacent tiles.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Spacing only rejects identical cells.

THE FAILURE

Spacing only rejects identical cells.

Unsuccessful approach: Manhattan spacing still admits diagonally touching spawns.

Case contract

Candidates [row, col] are tried in order until count spawns are chosen. A spawn must be in bounds on a '.' tile, at Chebyshev distance >= min_dist from the player and at Chebyshev distance >= 2 from every chosen spawn (no touching spawns, diagonals included). Returns chosen cells.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(grid, player, candidates, min_dist, count):
    chosen = []
    pr, pc = player
    for r, c in candidates:
        if len(chosen) >= count:
            break
        if not (0 <= r < len(grid) and 0 <= c < len(grid[0])) or grid[r][c] != '.':
            continue
        if max(abs(r - pr), abs(c - pc)) < min_dist:
            continue
        if any(max(abs(r - a), abs(c - b)) < 1 for a, b in chosen):
            continue
        chosen.append([r, c])
    return chosen
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['...#', '.#..', '#.#~', '~~.~', '~~#.', '~##.', '....', '...#'],
    [1, 2],
    [[0, 1], [6, 4], [5, 4], [4, 1], [4, 0], [6, 1], [0, 4], [7, 2], [5, 3], [-1, 1]],
    3,
    2],
   [[6, 1], [5, 3]]),
  ('fault site spawn spacing #1',
   [['.~.', '#..', '.#.', '...', '..#', '.~.', '#..', '~..'],
    [0, 2],
    [[3, 3], [3, 1], [3, 0], [7, -1], [4, 3], [7, 1]],
    3,
    2],
   [[3, 1], [7, 1]]),
  ('regression spawn spacing #2',
   [['...#.#', '~.#...', '...#..', '......', '.~..~.', '#...#.', '....~.'],
    [2, 4],
    [[3, 4], [0, 0], [4, 3], [1, 0], [3, 2], [3, 0], [7, 0], [7, 6]],
    0,
    5],
   [[3, 4], [0, 0], [3, 2], [3, 0]]),
  ('regression spawn spacing #3',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('fault site spawn spacing #1',
   [['.~.', '#..', '.#.', '...', '..#', '.~.', '#..', '~..'],
    [0, 2],
    [[3, 3], [3, 1], [3, 0], [7, -1], [4, 3], [7, 1]],
    3,
    2],
   [[3, 1], [7, 1]]),
  ('regression spawn spacing #1',
   [['...#.#', '~.#...', '...#..', '......', '.~..~.', '#...#.', '....~.'],
    [2, 4],
    [[3, 4], [0, 0], [4, 3], [1, 0], [3, 2], [3, 0], [7, 0], [7, 6]],
    0,
    5],
   [[3, 4], [0, 0], [3, 2], [3, 0]]),
  ('regression spawn spacing #2',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('regression spawn spacing #3',
   [['...#.~..', '.#~.....', '.......#', '#...#..#'],
    [0, 3],
    [[4, -1], [2, 6], [-1, 6], [4, 8], [-1, -1], [1, -1], [1, -1], [2, 8], [4, 2], [3, 5]],
    1,
    2],
   [[2, 6]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('regression spawn spacing #2',
   [['...#.~..', '.#~.....', '.......#', '#...#..#'],
    [0, 3],
    [[4, -1], [2, 6], [-1, 6], [4, 8], [-1, -1], [1, -1], [1, -1], [2, 8], [4, 2], [3, 5]],
    1,
    2],
   [[2, 6]]),
  ('regression spawn spacing #3',
   [['.~..', '#...', '..~.'],
    [0, 2],
    [[1, 0], [3, -1], [1, 2], [-1, 1], [1, 3], [3, 0], [1, 0], [2, 1]],
    1,
    5],
   [[1, 2]]),
  ('regression spawn spacing #4',
   [['...', '~..', '#~~', '...'],
    [2, 1],
    [[0, 2], [2, -1], [1, 1], [2, 1], [2, 1], [3, -1], [2, -1], [2, 1], [-1, 3], [-1, -1]],
    0,
    3],
   [[0, 2]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['.~..', '#...', '..~.'],
    [0, 2],
    [[1, 0], [3, -1], [1, 2], [-1, 1], [1, 3], [3, 0], [1, 0], [2, 1]],
    1,
    5],
   [[1, 2]]),
  ('regression spawn spacing #2',
   [['...', '~..', '#~~', '...'],
    [2, 1],
    [[0, 2], [2, -1], [1, 1], [2, 1], [2, 1], [3, -1], [2, -1], [2, 1], [-1, 3], [-1, -1]],
    0,
    3],
   [[0, 2]]),
  ('regression spawn spacing #3',
   [['..#..', '.#..~', '.##..', '~...#'], [2, 3], [[2, 1], [0, 1], [4, 3], [1, 2], [1, 0]], 0, 5],
   [[0, 1]]),
  ('regression spawn spacing #4',
   [['.#~', '.#.', '~..', '.#.', '.#.', '.##', '...'], [3, 1], [[5, 2], [1, 0], [1, 1], [2, 1]], 1, 2],
   [[1, 0]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['.#~', '...', '~.#', '#.~', '..#', '#~.'], [3, 1], [[5, 0], [1, 0], [6, -1], [6, -1]], 0, 5],
   [[1, 0]])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('fault site spawn spacing #1',
   [['...', '..#', '..~', '..#', '.~.', '...', '.~.', '.~#'],
    [7, 1],
    [[6, 3], [-1, 0], [2, 1], [7, 1], [3, 1]],
    3,
    5],
   [[2, 1]]),
  ('fault site spawn spacing #2',
   [['..~.~', '..#..', '.~...', '..~.~', '.~#..', '.....', '.....'],
    [0, 2],
    [[2, 0], [4, 5], [5, 0], [0, 5], [5, 4], [7, 1], [-1, -1], [4, 0], [7, 3]],
    3,
    3],
   [[5, 0], [5, 4]]),
  ('regression spawn spacing #1',
   [['.#~', '.#.', '~..', '.#.', '.#.', '.##', '...'], [3, 1], [[5, 2], [1, 0], [1, 1], [2, 1]], 1, 2],
   [[1, 0]]),
  ('regression spawn spacing #2',
   [['#.......', '.~~..#.#', '.~......', '.#......', '..#~#...', '#.##..~.', '......~.', '.##...##'],
    [6, 3],
    [[0, -1], [4, 0], [1, 3], [3, 8], [5, 1], [1, -1], [5, 3], [6, 2], [0, 0], [-1, 4]],
    2,
    5],
   [[4, 0], [1, 3]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['...#...', '......~', '~~.....', '..~....', '.~....~', '.....#.'], [5, 2], [[1, 5]], 0, 0],
   [])]]
for label, args, expected in cases[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
diagonal neighbour spawn #1[[1, 2], [2, 3]][[1, 2]]Failed
regression spawn spacing #1[[6, 1], [7, 2]][[6, 1], [5, 3]]Failed
fault site spawn spacing #1[[3, 1], [3, 0]][[3, 1], [7, 1]]Failed
regression spawn spacing #2[[3, 4], [0, 0], [4, 3], [3, 2], [3, 0]][[3, 4], [0, 0], [3, 2], [3, 0]]Failed
regression spawn spacing #3[[0, 3], [0, 0], [1, 1]][[0, 3], [0, 0], [2, 4]]Failed
exact safe radius #1[[0, 2]][[0, 2]]Passed
negative index candidate #1[[2, 0]][[2, 0]]Passed
control #1[][]Passed

SHA-256 / 5bbcdbba0eca32a6b93180dfd76586779667516d6e4235c7191e55c1f9659cc9

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(grid, player, candidates, min_dist, count):
    chosen = []
    pr, pc = player
    for r, c in candidates:
        if len(chosen) >= count:
            break
        if not (0 <= r < len(grid) and 0 <= c < len(grid[0])) or grid[r][c] != '.':
            continue
        if max(abs(r - pr), abs(c - pc)) < min_dist:
            continue
        if any(abs(r - a) + abs(c - b) < 2 for a, b in chosen):
            continue
        chosen.append([r, c])
    return chosen
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['...#', '.#..', '#.#~', '~~.~', '~~#.', '~##.', '....', '...#'],
    [1, 2],
    [[0, 1], [6, 4], [5, 4], [4, 1], [4, 0], [6, 1], [0, 4], [7, 2], [5, 3], [-1, 1]],
    3,
    2],
   [[6, 1], [5, 3]]),
  ('fault site spawn spacing #1',
   [['.~.', '#..', '.#.', '...', '..#', '.~.', '#..', '~..'],
    [0, 2],
    [[3, 3], [3, 1], [3, 0], [7, -1], [4, 3], [7, 1]],
    3,
    2],
   [[3, 1], [7, 1]]),
  ('regression spawn spacing #2',
   [['...#.#', '~.#...', '...#..', '......', '.~..~.', '#...#.', '....~.'],
    [2, 4],
    [[3, 4], [0, 0], [4, 3], [1, 0], [3, 2], [3, 0], [7, 0], [7, 6]],
    0,
    5],
   [[3, 4], [0, 0], [3, 2], [3, 0]]),
  ('regression spawn spacing #3',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('fault site spawn spacing #1',
   [['.~.', '#..', '.#.', '...', '..#', '.~.', '#..', '~..'],
    [0, 2],
    [[3, 3], [3, 1], [3, 0], [7, -1], [4, 3], [7, 1]],
    3,
    2],
   [[3, 1], [7, 1]]),
  ('regression spawn spacing #1',
   [['...#.#', '~.#...', '...#..', '......', '.~..~.', '#...#.', '....~.'],
    [2, 4],
    [[3, 4], [0, 0], [4, 3], [1, 0], [3, 2], [3, 0], [7, 0], [7, 6]],
    0,
    5],
   [[3, 4], [0, 0], [3, 2], [3, 0]]),
  ('regression spawn spacing #2',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('regression spawn spacing #3',
   [['...#.~..', '.#~.....', '.......#', '#...#..#'],
    [0, 3],
    [[4, -1], [2, 6], [-1, 6], [4, 8], [-1, -1], [1, -1], [1, -1], [2, 8], [4, 2], [3, 5]],
    1,
    2],
   [[2, 6]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['..~...', '#.~...', '.#....'],
    [0, 5],
    [[0, 3], [0, 0], [1, 1], [3, 3], [2, 1], [0, 1], [0, 5], [2, 4], [2, 3], [1, 4]],
    1,
    3],
   [[0, 3], [0, 0], [2, 4]]),
  ('regression spawn spacing #2',
   [['...#.~..', '.#~.....', '.......#', '#...#..#'],
    [0, 3],
    [[4, -1], [2, 6], [-1, 6], [4, 8], [-1, -1], [1, -1], [1, -1], [2, 8], [4, 2], [3, 5]],
    1,
    2],
   [[2, 6]]),
  ('regression spawn spacing #3',
   [['.~..', '#...', '..~.'],
    [0, 2],
    [[1, 0], [3, -1], [1, 2], [-1, 1], [1, 3], [3, 0], [1, 0], [2, 1]],
    1,
    5],
   [[1, 2]]),
  ('regression spawn spacing #4',
   [['...', '~..', '#~~', '...'],
    [2, 1],
    [[0, 2], [2, -1], [1, 1], [2, 1], [2, 1], [3, -1], [2, -1], [2, 1], [-1, 3], [-1, -1]],
    0,
    3],
   [[0, 2]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['#.#', '...', '#.#', '.#.', '...', '...', '...', '##.'], [6, 2], [[2, -1], [7, 2]], 0, 0],
   [])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('regression spawn spacing #1',
   [['.~..', '#...', '..~.'],
    [0, 2],
    [[1, 0], [3, -1], [1, 2], [-1, 1], [1, 3], [3, 0], [1, 0], [2, 1]],
    1,
    5],
   [[1, 2]]),
  ('regression spawn spacing #2',
   [['...', '~..', '#~~', '...'],
    [2, 1],
    [[0, 2], [2, -1], [1, 1], [2, 1], [2, 1], [3, -1], [2, -1], [2, 1], [-1, 3], [-1, -1]],
    0,
    3],
   [[0, 2]]),
  ('regression spawn spacing #3',
   [['..#..', '.#..~', '.##..', '~...#'], [2, 3], [[2, 1], [0, 1], [4, 3], [1, 2], [1, 0]], 0, 5],
   [[0, 1]]),
  ('regression spawn spacing #4',
   [['.#~', '.#.', '~..', '.#.', '.#.', '.##', '...'], [3, 1], [[5, 2], [1, 0], [1, 1], [2, 1]], 1, 2],
   [[1, 0]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['.#~', '...', '~.#', '#.~', '..#', '#~.'], [3, 1], [[5, 0], [1, 0], [6, -1], [6, -1]], 0, 5],
   [[1, 0]])],
 [('diagonal neighbour spawn #1', [['....', '....', '....'], [0, 0], [[1, 2], [2, 3]], 1, 3], [[1, 2]]),
  ('fault site spawn spacing #1',
   [['...', '..#', '..~', '..#', '.~.', '...', '.~.', '.~#'],
    [7, 1],
    [[6, 3], [-1, 0], [2, 1], [7, 1], [3, 1]],
    3,
    5],
   [[2, 1]]),
  ('fault site spawn spacing #2',
   [['..~.~', '..#..', '.~...', '..~.~', '.~#..', '.....', '.....'],
    [0, 2],
    [[2, 0], [4, 5], [5, 0], [0, 5], [5, 4], [7, 1], [-1, -1], [4, 0], [7, 3]],
    3,
    3],
   [[5, 0], [5, 4]]),
  ('regression spawn spacing #1',
   [['.#~', '.#.', '~..', '.#.', '.#.', '.##', '...'], [3, 1], [[5, 2], [1, 0], [1, 1], [2, 1]], 1, 2],
   [[1, 0]]),
  ('regression spawn spacing #2',
   [['#.......', '.~~..#.#', '.~......', '.#......', '..#~#...', '#.##..~.', '......~.', '.##...##'],
    [6, 3],
    [[0, -1], [4, 0], [1, 3], [3, 8], [5, 1], [1, -1], [5, 3], [6, 2], [0, 0], [-1, 4]],
    2,
    5],
   [[4, 0], [1, 3]]),
  ('exact safe radius #1', [['.....', '.....'], [0, 0], [[1, 1], [0, 2]], 2, 2], [[0, 2]]),
  ('negative index candidate #1', [['...', '...', '..#'], [0, 0], [[-1, -1], [2, 0]], 1, 2], [[2, 0]]),
  ('control #1',
   [['...#...', '......~', '~~.....', '..~....', '.~....~', '.....#.'], [5, 2], [[1, 5]], 0, 0],
   [])]]
for label, args, expected in cases[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
diagonal neighbour spawn #1[[1, 2], [2, 3]][[1, 2]]Failed
regression spawn spacing #1[[6, 1], [7, 2]][[6, 1], [5, 3]]Failed
fault site spawn spacing #1[[3, 1], [7, 1]][[3, 1], [7, 1]]Passed
regression spawn spacing #2[[3, 4], [0, 0], [4, 3], [3, 2], [3, 0]][[3, 4], [0, 0], [3, 2], [3, 0]]Failed
regression spawn spacing #3[[0, 3], [0, 0], [1, 1]][[0, 3], [0, 0], [2, 4]]Failed
exact safe radius #1[[0, 2]][[0, 2]]Passed
negative index candidate #1[[2, 0]][[2, 0]]Passed
control #1[][]Passed

SHA-256 / 2e8641b550d6971be9d72b05922d3bdaabb63f7064e64bc26ae5616ffce8909e

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Deterministic toy contract stipulated for this model; integer or exact arithmetic only, not a reproduction of any specific game engine. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:50:49.547025+00:00.

Case digest / 8a29a2f67243ddb79b435840e1dac2f35809f253b0b42732c8124da3346fdfd3