The world of Metro: Last Light isn’t pretty. To escape nuclear war, millions of the game’s Russian citizens descended into subway stations the instant the air raid sirens cried out, forced to leave their lives on the surface behind. Below ground, life is bleak. The irradiated world above means no access to fresh air or sunshine. Money means nothing, and ammunition is currency. Fathers nearly break down when sons ask where Mom is and when she’s coming home—and they have to repeat a variation of the same lie they’ve told for countless years. Radioactive mutants attack the subterranean train-station-based encampments.

The setting is easy to buy into because few blinking indicators and status updates slap you in the face, offering constant reminds that you’re playing a video game. This is deliberate, according to Andrey Prokhorov, creative director and co-founder at 4A Games, the studio behind Metro 2033 and Metro: Last Light.

“If you look at your monitor (or TV set) as a gate into the world of the game, the heads-up display (HUD) elements become the bars keeping you from entering that world,” he told Ars in a recent interview. And it's part of a trend.

In the beginning

HUD-free and HUD-minimal games came to prominence near the beginning of the current generation of console hardware. In 2005, gamers and press were baffled when the first-person game based on Peter Jackson’s King Kong debuted. Unlike most similar games before it, the game didn’t feature a health meter, ammo readout, or objective waypoint popping up to indicate that the opening cut scene had ended and the “game” had begun. Instead, this gameplay information was presented organically within the game’s world.

The only way to see how much ammo remained in a clip in King Kong was to count your shots or actually examine the gun you were holding. This crucial design decision, almost unheard of at the time, eliminated the barrier between the game-engine story sequences and the actual gameplay. And it was awesome.

2006’s Fight Night Round 3 similarly stripped away the HUD completely, removing the ubiquitous on-screen display for health and stamina that had been seen in almost every fighting game before it. Instead of monitoring a flashing red health bar, Round 3 forced players to watch how their pugilist acted—the way he’d labor between jabs or shuffle around the ring more slowly than at the start of the round.

A close-tucked camera trained on the fighters’ faces did the health meter’s job, highlighting that gushing cut above the left eyebrow and a swollen-shut right eye. This wouldn’t necessarily work in a more abstract game like Street Fighter or Mortal Kombat, but it paid off in spades for a more realistic take on fighting like Round 3.

That was nothing, though, compared to the dramatic HUD reductions of Splinter Cell: Conviction. Early games in the series had an on-screen meter for practically everything: visibility, ambient noise level, player frustration, mission objectives, etc. Conviction wiped all that away, putting everything into the game’s environment.

When protagonist Sam Fisher was out of sight, the screen would go black and white. Getting spotted marked the return of color and saturation in an instant. Giant text and video displayed in a not so subtle way within the game world told players where to go and what they needed to do next. The result was a startling departure from the past that got smarter and more stylish as a result.

Stuck on me

These were just some of the experiments in largely HUD-free design that helped inspire the Metro games. “I can’t really say exactly when the idea of minimalistic HUD occurred to us and whose idea it was,” Prokhorov said. He added that 4A arrived at the HUD-free approach gradually and were building it from 2006 to 2008 when the team was working on 2033.

In Metro, you know when the filters on your gas mask need changing because water starts collecting on the visor or the goggles start fogging up. Your breathing gets shallower and faster as the surrounding poison clogs the only thing between your lungs and the long nuclear winter. The ever-ticking watch on your left wrist counts down the seconds to your expiration, too, but you have to actively push a button to look at it; it isn’t constantly displayed in a corner of the screen, just as a watch isn’t constantly in the corner of your vision.

With the recent trend toward more realism in games, you’d think more designers would be opting for this kind of minimal-HUD approach. But according to Prokhorov, developers often simply don’t have the time to integrate all this information in a natural way.

“[Traditional HUD elements are] just simple and reliable,” Prokhorov said. “They make absolutely sure that the player understands everything. It’s the easy way out. In no way can you save yourself effort by minimizing the HUD. On the contrary, it takes even more.”

For example, he noted, it’s easier to just draw a compass on-screen than to use contextual clues to nudge the player toward the next objective. “Making subtle lighting cues in the environment work in a manner that gives the player an idea of where to go next takes a lot more time and effort,” he said. “But it can be done, and I wouldn’t say it’s that much of a problem.”

Why it works

In a game like Crysis or Halo, the player character represents the pinnacle of military technology. It makes sense that the armored suits have on-screen readouts for shields, ammo, objective waypoints and the like. It also makes sense that you as a player would see that stuff inside the character’s helmet. But in the austere universe of Metro, where atomic bombs have sent the world back to a technological Stone Age, the HUD has to reinforce the state of the world.

“Our protagonist has virtually no access to anything high-tech, so such a HUD would destroy the atmosphere,” Prokhorov said.

Going with a HUD-free approach can have a profound effect on the kind of atmosphere a developer creates with a game. Everything in a Metro game revolves around the player’s vulnerability and uncertainty. In the middle of a firefight, you have to remember to reload. You have to know how much ammo you have left. You have to know if you have any spare weapons. It isn’t until you pull the trigger that the actual ammo readout comes onscreen. Before that, you have to gauge it by looking at the spaces in the gun models’ exposed clip or chambers. It’s much slower and more deliberate, as Metro is more about atmosphere than it is about killing mutants or humans.

Keep it simple, stupid

The trade-offs to make a game HUD-free won’t work for everything. A HUD-free MMO would be nearly impossible, as would a tactical shooter without a tactical display. There’s simply too much information that needs to be conveyed to the player at a moment’s notice in these genres.

But as technology progresses, we’ll likely see more of the action and less of the HUD distractions. Just look at the re-release of The Legend of Zelda: Ocarina of Time for 3DS. Everything that once cluttered the screen now resides on the system’s ancillary display, leaving the main view free and clear.

Prokhorov said he’d rather not make predictions about the future of interface design because the pace of technology makes any attempt at it pointless. That said, he’s sure the continued development of player interfaces, including new controllers, will make HUD removal easier.

“We could have made Last Light totally HUDless, but we didn’t have quite enough time for that,” he said.