This week the Gene Siskel Film Center will celebrate experimental filmmaker Robert Nelson, who died earlier this year at the age of 81, by screening programs of his work tomorrow at 6 PM and on Saturday at 12:30 PM. As Bruce Weber wrote in his New York Times obituary, Nelson “brought spontaneity, teasing, and wit to the often deadly serious arena of avant-garde moviemaking,” though it should be noted he possessed a strong formal sensibility as well. His early short Oh Dem Watermelons (1965)—which you can watch on YouTube, remarkably—sets the tone for much of his film art: that work features gags of watermelons exploding as well as a curious score by tape-loop pioneer Steve Reich, both of which serve to mock racist conventions in American popular culture. Nelson often regarded art as a game, a sentiment reflected in one of his most respected works, Bleu Shut (1970). That piece pokes fun at spectators’ impatience with experimental cinema by having an on-screen clock count down the film’s running time.