func (m *PU_Map) AddTile(_x int, _y int) *PU_Tile {
var index int64 = pos.Hash(_x, _y, 0)
tile, present := m.tileMap[index]
if !present {
tile = NewTile(_x, _y)
m.tileMap[index] = tile
}
return tile
}
func (m *PU_Map) GetTile(_x int, _y int) *PU_Tile {
var index int64 = pos.Hash(_x, _y, 0)
tile := m.tileMap[index]
return tile
}