@Firstaide gameplay wise DN3d is a good capable shooter and for the time the engine was pretty good. It quite cleverly used tricks to get around having sectors (level geometry) overlapping in a 2.5D engine allowing for visible tunnels and such in a couple ways (one used "solid" sprites that could be walked on and shot at, and the other used invisible teleports (which it also used for water you could swim in and 'long falls'). DNF again, capable fps game, but the story and writing just suuuck.