each wall (excluding the exterior one) have a width of at least 2 (can be filled with FIT tiles)
RGB code:
GRD	0	0	0       // ground tile
GCF	255	0	255     // ghost cell floor tile
WAL	0	0	255     // wall tile
GSD	0	255	0       // ghost door tile
GWL	0	255	255     // ghost wall tile
TPT	255	0	0       // teleporter tile
FIT	255	255	255     // fully inaccessible tile (tiles between walls)