The Doom engine represents levels internally using structures called linedefs, sidedefs, sectors, verticies, and things (meaning monsters, items, decorations, etc.). The doom engine reads levels and other data from a file called a WAD.
ð ə WORD_BOUNDARY d uː m WORD_BOUNDARY ɛ n d̠ʒ ɪ n WORD_BOUNDARY ɹ ɛ p ɹ ɪ z ɛ n t s WORD_BOUNDARY l ɛ v ə l z WORD_BOUNDARY ɪ n t ɜː n ə l i WORD_BOUNDARY j uː z ɪ ŋ WORD_BOUNDARY s t ɹ ʌ k t̠ʃ ə ɹ z WORD_BOUNDARY k ɔ l d WORD_BOUNDARY l aɪ n d ɛ f s WORD_BOUNDARY s aɪ d d ɛ f s WORD_BOUNDARY s ɛ k t ə ɹ z WORD_BOUNDARY v ɜː t ɪ s i z WORD_BOUNDARY æ n d WORD_BOUNDARY θ ɪ ŋ z WORD_BOUNDARY m iː n ɪ ŋ WORD_BOUNDARY m ɔ n s t ə ɹ z WORD_BOUNDARY aɪ t ə m z WORD_BOUNDARY d ɛ k ə ɹ ɹ eɪ ʃ ə n z WORD_BOUNDARY ɛ t s ɛ t ɹ ə WORD_BOUNDARY ð ə WORD_BOUNDARY d uː m WORD_BOUNDARY ɛ n d̠ʒ ɪ n WORD_BOUNDARY ɹ iː d z WORD_BOUNDARY l ɛ v ə l z WORD_BOUNDARY æ n d WORD_BOUNDARY ʌ ð ə ɹ WORD_BOUNDARY d eɪ t ə WORD_BOUNDARY f ɹ ʌ m WORD_BOUNDARY ʌ WORD_BOUNDARY f aɪ l WORD_BOUNDARY k ɔ l d WORD_BOUNDARY ʌ WORD_BOUNDARY d ʌ b ə l j uː eɪ d iː WORD_BOUNDARY