Hidden line elimination was a research challenge, surfaces were not drawn at all, and multiple windows, whether overlapping or tiled, were a dream for the future .-- T 21 : 04, 7 December 2006 ( UTC)
12.
The North Korean government supposedly bought more than twice the number of trainsets required for daily use, prompting speculation that the metro might contain hidden lines and / or stations that are not open to the public.
