Feeling beaten down by the news? Why not watch a documentary on gerrymandering to cheer you up? “Slay the Dragon,” by Chris Durrance and Barak Goodman, deftly outlines how redistricting has eroded American democracy and helped usher compromise out of our legislatures. It’s a level-headed documentary about an unlevel playing field that traces the scope and magnitude of district map-drawing for political gain. “Slay the Dragon,” which will be available on-demand and in digital release Friday after having its theatrical release canceled by the coronavirus, may not be the most heartening portrait of our political system. But it’s a vital one and it provides reasons for optimism, too. Aside from laying out the strategies and manipulations of gerrymandering, it tracks a handful of those fighting its practice, including the lawyers whose case rises to the Supreme Court and a humble Michigan woman named Katie Fahey. She turns almost accidental activist when a Facebook post leads to the creation of a grassroots campaign to put Michigan’s district drawing in the hands of a bipartisan citizen commission – a practice now used, in some form, in 21 states. But most states have their maps drawn up by their own state legislatures every 10 years, an approach that can breed obvious conflicts of interest. Gerrymandering has been around for more than 200 years. Its name comes from a Massachusetts redistricting that gave early 19th century Boston-area districts the appearance of a salamander. Its long been a tool of both parties, though “Slay the Dragon” is focused on the Republican efforts to win state houses in the 2010 election with the intent to redraw maps. It was a hugely successful effort (some of the key strategists are interviewed here) that led to the flipping of 11 state legislatures. The subsequent redistricting created its own assortment of oddly shaped maps: a “snake” in North Carolina, an “upside down elephant” in Texas, a “praying mantis” in Maryland. Redistricting can have the result of quarantining the votes of one party or one demographic, thus muting the political power of potentially a larger portion of the public and essentially preordaining that a party will hold certain congressional seats. Several of North Carolina’s districts, in a map that has since been ruled to have violated the state constitution, were 55% or 57% African American. “Slay the Dragon” seeks to draw the connections between such seeming governmental minutia with much broader policy and political effects. The filmmakers explain how Michigan’s redistricting played a pivotal role in the Flint Water crisis, how Wisconsin’s redrawn districts fueled the divisive agenda of former Wisconsin Gov. Scott Walker and how such maps potentially aided the election of Donald Trump in 2016. The movie is ultimately an effort to take something arcane and make it clear – to read between the lines, so to speak. No one will mistake the politics of “Slay the Dragon”; it’s clearly liberal-leaning. But the aims of the documentary’s characters aren’t in themselves political: they want votes to count. And they don’t want Washington operators remaking their districts. “Slay the Dragon,” a Magnolia Pictures release, is rated PG-13 by the Motion Picture Association of America for brief strong language. Running time: 101 minutes. Three stars out of four.