#include <queue>
static void CreateDesertOrRainForest()
{
    TileIndex update_freq = MapSize() / 8;
    uint max_desert_height = CeilDiv(_settings_game.construction.max_heightlevel, 4);
    std::queue<std::pair<TileIndex, TileIndex>> queue;

    for (TileIndex tile = 0; tile != MapSize(); ++tile) {
        if ((tile % update_freq) == 0) IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);

        if (!IsValidTile(tile)) continue;

        if ((TileHeight(tile) >= max_desert_height || IsTileType(tile, MP_WATER))) {
            SetTropicZone(tile, TROPICZONE_RAINFOREST);
            queue.push(std::make_pair(tile, tile));
        } else {
            SetTropicZone(tile, TROPICZONE_DESERT);
        }
    }

    static const TileIndexDiffC NEIGHBORS[] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    while (!queue.empty()) {
        auto p = queue.front();
        queue.pop();
        for (auto &d : NEIGHBORS) {
            auto t = AddTileIndexDiffCWrap(p.second, d);
            if (t == INVALID_TILE) continue;
            if (GetTropicZone(t) != TROPICZONE_DESERT) continue;

            auto dist = DistanceSquare(t, p.first);
            if (dist < 49) {
                queue.push(std::make_pair(p.first, t));
                SetTropicZone(t, dist < 4 ? TROPICZONE_RAINFOREST : TROPICZONE_NORMAL);
            }
        }
    }

    for (uint i = 0; i != 256; i++) {
        if ((i % 64) == 0) IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);

        RunTileLoop();
    }
}