There are so many different and varied flavors of the apocalypse film: the spectacle of a disaster movie à la Roland Emmerich, or the punky desert chic of a "Mad Max" movie.

There's also the lo-fi take, the kind of stripped-down indie films in which people experience the apocalypse from afar, with themes of life, death and survival that resonate in a more existential, philosophical register, rather than the action-packed flicks that imagine the end of the world as something more immediate and violent.

Mel Eslyn's directorial debut "Biosphere" fits squarely into this sub-genre, in which the apocalypse has already happened off-screen and we don't need too much information to get up to speed. The setting and circumstances merely set the stage upon which an intimate moral quandary plays out. The surroundings and events are merely a conduit to pose a "what would you do" type of question.

The players are the two inhabitants of a biosphere sealed off from the toxic outside world, a self-sustaining geodesic dome, with a hydroponic garden as a food source. We meet Ray (Sterling K. Brown) and Billy (Mark Duplass) on their morning jog around the dome's inner perimeter, as Billy lobs questions and theories about the relationship between brothers Mario and Luigi from "Super Mario Bros" and Ray calmly volleys back.

This conversation is captured in one long shot around the room, which illustrates both the space, and what we're in for with "Biosphere," a smart, wordy, esoteric chamber piece infused with references from video games to literature to help underline the relationship between the two men. Ray is the serious, rational one and Billy is the emotional, wacky one. Shockingly (or perhaps not), Billy reveals that he used to be the president and is responsible for this whole mess in the first place.

The script, by Duplass and Eslyn, reveals all these little nuggets of crucial information in long conversations, fiery spats, and comedic riffs between Ray and Billy. It's clear they've been here a long time and are settled into their routine. But for this story to unfold in a way that's not just two guys talking about video games in a dome, we're going to need a little conflict.

Enter Sam, one of the fish fertilizing the hydroponic garden, who turns up dead. After enjoying Sam for dinner, Ray reluctantly informs Billy that they actually ate Diane, the last female fish. Without the fish reproducing, there will be no food, and they will die. The news sends Billy into a tailspin, until Ray notices that another male fish, Norm, is starting to exhibit some interesting changes, transitioning from male to female before their very eyes in response to this threat of extinction.

This high-concept setting is a chance to comment on contemporary culture, including our shifting understanding of gender and sexuality.

It's an interesting premise, and Brown and Duplass hold the screen well together and apart. But a good idea and good actors don't necessarily make for a truly compelling feature film. All of the elements are there — writing, performance, themes — but there's not enough plot to sustain an hour and 45 minute feature.

As the situation escalates, it becomes clear that they don't quite know where or how to end things, and it lands with a thud. A fascinating curio that speaks to many contemporary issues, "Biosphere" feels like a rough draft, as it hasn't been honed to a degree that allows it to fully penetrate.

'Biosphere'

2 stars out of 4

No MPA rating

Where: In theaters and On Demand Friday.