for(int tx = left; tx <= right; tx++) {
if(tx < 0 || tx >= levels) continue;
for(int ty = top; ty <= bottom; ty++) {
if(ty < 0 || ty >= levels) continue;
TileKey tile = new TileKey(level, tx, ty);
double y = (double)ty - (double)levels/2; // In level 0 we have only one tile
for(int tx = left; tx <= right; tx++) {
if(tx < 0 || tx >= levels) continue;
for(int ty = top; ty <= bottom; ty++) {
if(ty < 0 || ty >= levels) continue;
TileKey tile = new TileKey(level, tx, ty);
double y = (double)ty - (double)levels/2; // In level 0 we have only one tile