When Theatermakers Long for the Stage, Playfully Two short films that find pandemic-sidelined performers grappling with Beckett are a highlight of the annual Exponential Festival. Lucy Kaminsky in “The Puzzlers 2: Black Box.”Credit...via The Exponential Festival “These films were made by theater people.” It’s just one line of text on the Exponential Festival website, explaining the provenance of a pair of video shorts in the lineup: zestfully odd and playful mash-ups of the first piece in Samuel Beckett’s doom-laden prose collection “Texts for Nothing,” from a company called Accent Wall Productions. Yet that simple declarative statement gets to the crux of the matter, which is that the experimental artists behind “The Puzzlers” and “The Puzzlers 2: Black Box” — notably including Jess Barbagallo and Emily Davis — know who they are, which shut-down art form they miss with a piercing longing and which different kind of work they’re making in the meantime.