A Midsummer Night’s Dream, streamlined to 90 minutes and staged outdoors by Classical Theatre of Harlem, is as cool and fizzy as a glass of Prosecco. Judging by the wild guffaws and applause on opening night, the zanies who populate this most fanciful of Shakespeare’s comedies (embodied by a top-flight cast of youthful New York actors) kept a steady hold on playgoers’ attention, despite the distraction of sirens punctuating the Bard’s iambic pentameter, helicopters overhead, and heat only slightly below the day’s high of 90 degrees Fahrenheit. At a dramatic moment, an explosion of amateur fireworks just outside the amphitheater added a fortuitous burst of red and orange to the twilit sky, eliciting a gasp of audience amusement.