pos_start = yx_to_map_pos(yx_start);
fov_map[pos_start] = fov_map[pos_start] | SHADOW_LEFT | SHADOW_RIGHT;
fill_shadow(yx_eye, yx_start, fov_map, pos_a, pos_b);
pos_start = yx_to_map_pos(yx_start);
fov_map[pos_start] = fov_map[pos_start] | SHADOW_LEFT | SHADOW_RIGHT;
fill_shadow(yx_eye, yx_start, fov_map, pos_a, pos_b);