▁considered ▁to ▁be ▁Duke ▁N uk em ▁ 3 D , ▁Sh adow ▁War rior , ▁and ▁Blood . ▁ ▁Techn ical ▁features ▁ ▁S ectors ▁ ▁S ectors ▁are ▁the ▁building ▁blocks ▁of ▁a ▁level ' s ▁layout , ▁consisting ▁of ▁a ▁two - dimensional ▁pol yg onal ▁outline ▁when ▁viewed ▁from ▁above , ▁with ▁the ▁top ▁and ▁bottom ▁faces ▁of ▁the ▁sector ▁given ▁separate ▁alt itudes ▁to ▁create ▁a ▁three - dimensional ▁space . ▁Hence , ▁all ▁walls ▁are ▁perfectly ▁vertical — any thing ▁appearing ▁otherwise ▁is ▁techn ically ▁a ▁s loped ▁floor ▁or ▁ce iling . ▁The ▁word ▁room ▁can ▁be ▁used ▁as ▁a ▁loose ▁substitute ▁to ▁aid ▁understanding , ▁though ▁one ▁room ▁in ▁the ▁game ▁world ▁can ▁consist ▁of ▁many ▁se ctors , ▁and ▁par alla x ed ▁sk ies ▁can ▁give ▁the ▁ill usion ▁of ▁being ▁out do ors . ▁S ectors ▁can ▁be ▁manip ulated ▁in ▁real - time ; ▁all ▁of ▁their ▁attributes ▁such ▁as ▁shape , ▁height , ▁and ▁slope ▁could ▁be ▁modified ▁" on - the - fly " ▁by ▁games , ▁unlike ▁the ▁earlier ▁Do om ▁engine . ▁This ▁allowed ▁games ▁to ▁have ▁destruct ible ▁environments , ▁such ▁as ▁those ▁seen ▁in ▁Blood . ▁This ▁technique ▁is ▁similar ▁to ▁the ▁use ▁of ▁push ▁walls ▁in ▁the ▁earlier ▁Ap og ee ▁Software ▁title ▁R ise ▁of ▁the ▁Tri ad ▁which ▁featured ▁similar ▁dynamic ▁environments . ▁ ▁Develop ers ▁of ▁games ▁based ▁on ▁the ▁engine ▁used ▁special ▁reserved ▁" spr ites " ▁( game ▁objects