#define PREFERRED_TILE_SIZE 32
#define TILE_SIZE (ds->tilesize)
#define DOT_SIZE (TILE_SIZE / 4)
-#define EDGE_THICKNESS (TILE_SIZE / 16)
+#define EDGE_THICKNESS (max(TILE_SIZE / 16, 2))
#define BORDER TILE_SIZE
#define COORD(x) ( (x) * TILE_SIZE + BORDER )