Past continuous

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/pascon1.htm

http://www.englishexercises.org/makeagame/viewgame.asp?id=3798

http://www.englishexercises.org/makeagame/viewgame.asp?id=5600

http://www.englisch-hilfen.de/en/exercises/tenses/past_progressive_negation_sentences.htm