When times are tough, sometimes a burger has to stand as a complete dinner. That's where the $3.99 double cheeseburger at the Humdinger — a 52-year-old urban drive-in that has outlasted most of the other buildings on this forlorn stretch of Ninth Street — scores beautifully. One generous sandwich offers most of the basic food groups: meat (two beef patties), vegetables (lettuce and pickles), dairy (American cheese) and bread (a fluffy sesame-seed bun). Your burger meal is made to order by a staff enclosed behind a Plexiglas shield plastered with notices ("Be Nice to the Servers"), menu specials and terms of business (the Humdinger accepts only cash, but there is an ATM next to the video game). So, yeah, that means you have to take the burger home or eat it in the car, but that's where you keep your chips and your soda anyway.