TILE NUMBERING REFERENCE
========================

Reading order: LEFT to RIGHT, TOP to BOTTOM (same as reading text)

3x3 GRID (9 tiles, numbered 0-8):
┌───────┬───────┬───────┐
│       │       │       │
│   0   │   1   │   2   │
│       │       │       │
├───────┼───────┼───────┤
│       │       │       │
│   3   │   4   │   5   │
│       │       │       │
├───────┼───────┼───────┤
│       │       │       │
│   6   │   7   │   8   │
│       │       │       │
└───────┴───────┴───────┘

4x4 GRID (16 tiles, numbered 0-15):
┌─────┬─────┬─────┬─────┐
│  0  │  1  │  2  │  3  │
├─────┼─────┼─────┼─────┤
│  4  │  5  │  6  │  7  │
├─────┼─────┼─────┼─────┤
│  8  │  9  │ 10  │ 11  │
├─────┼─────┼─────┼─────┤
│ 12  │ 13  │ 14  │ 15  │
└─────┴─────┴─────┴─────┘

EXAMPLE:
If instruction is "Select all squares with buses" and buses are in:
- top-left tile → 0
- middle row middle → 4 (for 3x3) or 5 (for 4x4)
- bottom-right tile → 8 (for 3x3) or 15 (for 4x4)

INPUT FORMAT:
Type numbers separated by comma or space:
  2,5,6,8     (same as "2 5 6 8")
  skip        (if no matching tiles)
  done        (end the round early)