Based on a prize-winning 1932 short story by Marjorie Kinnan Rawlings about the battle of the sexes and a woman's revenge, Victor Nunez's "Gal Young Un" is a remarkably smooth low-budget ($100,000 production. Opening today at area theaters, it is witty and satisfying entertainment.

The heroine of "Gal Young Un" is Mattie Siles, a laconic, pipe-smoking widow residing on a secluded farm in the backwoods of northern Florida. She is wooed and won by a young opportunist named Trax, who comes across her property while hunting with a friend. Flattered by Trax's attentions and stirred by the prospect of having a man around the house, Mattie remarries, only to learn that she's stuck with a no-account companion.

Though charming and never physically abusive, Trax soon proves himself a scoundrel. He uses Mattie's isolated farmhouse as the base of a bootlegging operation. As the business prospers and expands, Mattie is left to supervise production at the still while Trax absents himself on selling trips. He returns from these trips acting more and more presumptuous.

At first Mattie keeps her peace. She doesn't protest when he shows up in fancy duds or a new roadster. It doesn't really bother her that the profits from the business never seem to trickle in her direction. She's still emotionally susceptible to Trax and reluctant to return to her loneliness. However, there's not much point in tolerating Trax's shenanigans when he begins treating her as an unpaid servant and using her home as a free boardinghouse. Trax overplays his hand when he turns up one day with a mistress, an oblivious teen-age waif named Elly, the "gal young un" of the title. This is a humiliation that Mattie won't tolerate, and while she bides her time and chooses precisely the right moment to put Trax in his place, she administers a comeuppance that is flawlessly executed.

Unlike the revenge exacted by the secretaries on their abusive boss in "Nine to Five," Mattie's treatment of Trax is never out of proportion. One feels a perfect comic restoration of the moral order. Mattie doesn't get any more satisfaction out of Trax than she requires. The sort of punishment Mattie dishes out fits the crime. A good deal of the pleasure one derives from the resolution of this ironically mismatched battle of the sexes is attributable to its sense of balance. The story is worked out so equitably that its sheer fairness becomes a source of unexpected humor.

Nunez, a former film teacher in the art department at Florida State University, served as the screenwriter, director, camera operator and supervising editor of this exemplary first feature.

Dana Preu, a tower of strength as Mattie, was recruited from the faculty of Florida A&M, where she teaches English. Her strong, rawboned face gives Nunez a powerfully attractive camera subject from the outset, and her performance grows more subtle as the story unfolds. She's never acted professionally before, and, marvelous and she is, one rather hopes that she'll quit on this singular note of triumph.

David Peck, a graduate student in direction in the Florida State drama department, seems a perfect embodiment of the charming, larcenous Trax. Even when relishing every detail of Mattie's fine-tuned revenge, it's impossible to hate Trax for his outrageous behavior, because his deviousness always seems pathetically funny. He's never figured to be a match for Mattie when the chips are down.

A young actress billed only as J. Smith projects considerable deadpan charm as the wayward, helpless Elly, whose fate gives the story an extra humorous kick. Confident in his material and performers, Nunez provides a crisp, compact framework in which the comedy can emerge with unforced precision and leave a memorable afterglow. The only bad habit Nunez reveals is an occasional reliance on excessively tight close-ups, perhaps a cropping problem resulting from the blowup of the original 16mm footage to 35mm. But as a rule, Nunez, like his heroine, demonstrates exceptional poise and wisdom at all the crucial moments.

"Gal Young Un" should enhance the friendly climate for independent American features. It if a triumph of resourceful small-scale filmmaking.