private void ParseSectors(Tokenizer levelTokens)
{
string token;
while ((token = levelTokens.GetNextToken()) != null) {
levelTokens.CheckThrow(token == "SECTOR", "Expected SECTOR!");
levelTokens.RequireNextInt();
Sector sector = ParseSectorHeader(levelTokens);
ParseSectorVertices(sector, levelTokens);
ParseSectorWalls(sector, levelTokens);
Sectors.Add(sector);
}
}