One Bullet At a Time

"This is your XQJ-37 plasma cannon. The only trouble is that since the old model XQJ was cobbled together from junked Amiga motherboards, you can only have one shot on the screen at a time."

- instruction sheet for Apeiron (a shareware Centipede clone by Ambrosia Software)

Guns in some games (space shooters especially) have a wildly fluctuating reload rate that suspiciously appears to be tied to the number of its bullets that are still on the screen. As soon as the bullet hits a wall or enemy (without ricocheting), or leaves the screen, another one is free to shoot.

How is such a thing possible? Perhaps you are armed only with the one bullet, which, much like a yo-yo, immediately returns upon leaving your line of sight.

More broadly, This is a general phenomenon where only a certain number of X are allowed to be present at one time; after that, you will either be prevented from creating new X, or the old X will start to vanish inexplicably. Typically this is done due to memory limitations. A good example of this is environment damage - you can only have so many bulletholes (for example, in Golden Eye 1997). Another example is new enemies not spawning until you kill some existing enemies. Bullets are simply the most obvious example, since it's pretty evident to players when a shot they tried to fire doesn't fire.

(Note: There is a plausible case to be made for a remotely-guided weapon system only being able to control N projectiles at once, such as the real-world Phoenix air-to-air missile deployed on the F-111 and F-14; but the space shooter bullets aren't guided.)

Most examples are Older Than the NES, although interestingly, the oldest video game did not have this limit. Outside of Retraux games, it's subjectively discredited at this point; the replacement is a firing rate, which prevents this from becoming an issue beyond a limited scope. The upside to this trope is that it can encourage players to get closer to enemies to do more damage, creating a risk\reward balance, or to prevent a certain tactic from being used exclusively.

Made possible by the Painfully-Slow Projectile. When applied to more permanent things, especially in Real Time Strategy games, it's an Arbitrary Headcount Limit.

Contrast Bullet Hell, where hundreds, possibly thousands of bullets can be on screen at once.


 * Primitive shoot'em ups follow this trope due to technical limitations:
 * Space Invaders may be the Trope Maker. This makes comebacks possible, as you can shoot more rapidly as the Invaders get closer... provided you don't miss, that is.
 * Gorf: Also applies to some enemy attacks. Unusually, you can fire again while one of your shots is still on screen, but your original shot disappears.
 * Mega Man can only have up to 3 bullets on screen at a time. Some special weapons in the sequels only allow one of its projectiles on the screen (e.g. Ice Wall). In the later games, you can even buy an upgrade to increase it to five shots on screen at a time.
 * His brother Proto Man, in part of the tradeoff for the slide and charge shot in Mega Man 9 (and presumably this applies in 10 as well), can only fire two shots at a time, though having the Proto Coil or Proto Jet equipped allows you to shoot three.
 * Mega Man Legends has this as a stat for guns called Energy which is the number of bullets on screen, while Rapid is how fast it can shoot said bullets.
 * Galaga only lets you shoot two bullets at a time.
 * Satans Hollow only allows one, but a weapon upgrade gives an additional shot and a second upgrade shoots a double/single alternating shot.
 * Contra has an upper limit, with the spread gun allowing 10 bullets on the screen. If you don't have enough for all five bullets, you can either get a 3-shot or single shot (as exploited in a tool assisted speedrun). Likewise, the laser was actually several parts of a shot fired at once, and if you fired while the first shot was still on screen, it would disappear, meaning if you tried to spam it, you'd have a very short range weapon on your hands.
 * All Shoot'em ups only allow one super-attack (smart bomb, nuke, etc.) at a time, either waiting until it finishes or after a fixed delay; in two player games, there might only be one on-screen bomb among the two players. Spamming bombs tends to be counter-productive depending on how the game works, either because the bomb blocks bullets, a short invulnerability is conferred, etc.
 * Asterax, a somewhat Asteroids-like old Mac shareware game, makes this the explicit benefit of buying better guns, with 4-12 shots from each player allowed on screen.
 * It's also present in many of Action 52 games. Some of them still avert it, allowing to spray numerous bullets, but this often causes the enemies or bosses to not spawn.
 * Not exactly a gun, but the original Super Mario Bros. did this with fireballs; only two could be out at a time.
 * Also applies to Super Mario World.
 * The Legend of Zelda had an upper limit to the amount of Sword Beams and arrows the player could unleash at a time.
 * And the N64 games both allow only one magical arrow to be shot at a time.
 * In Cave Story the number depends on the weapon. This also meant the Blade at level 2, which there can only be one on the screen at a time, deals insane amounts of damage in very close range (moreso than its level 3 version, whose projectiles don't disappear on contact) but there isn't anything outstanding otherwise.
 * Point blank fireball spam is also a very effective boss killer up until you get the knife (at least unless and until you get the machinegun)
 * Asteroids. Maximum of 4. In the Atari 2600 conversion, your limit is only two.
 * Hero Klungo Sssavesss Teh Universsse in Banjo-Kazooie Nuts & Bolts.
 * In Diablo, the sprite limit could be reached very easily with one Chain Lightning spell with many enemies in range or multiple Fire Wall spells. Sure, it's not a gun, but you still won't be able to cast any more until the effects finish up.
 * In Diablo II, you can cast as many missiles as you like ... but then you might not see them. Hilarity Ensues when fighting against a multi-shot lightning-enchanted boss while you have slow missiles active, where moving in the wrong direction (or not at all) will get you kill by hot air.
 * This happens to banana peels and the like in Mario Kart; the old ones disappear as new ones are placed.
 * A sprite-limit example: Milon's Secret Castle has keys which appear as sprites. If too many sprites (such as enemies) as already on the screen, the key won't be drawn; you have to clear out some of the enemies, leave the screen, and come back for the key to appear.
 * Team Fortress only allows eight pipebombs active at once. This limitation was added because some players tried filling the entire level with them to kill all hostiles at once; that and you'd probably hit the upper limit of ~600/768 entities in the original Quake engine. As such, this limit prevents spamming meant to kill off a full team in one swoop.
 * Also true for the sequel. The Sticky Launcher can still only place 8 bombs. If you shoot any more, first ones start detonating in sequence. The second launcher available, The Scottish Resistance, can have 14 bombs out at once, but will only detonate the ones you are actually aiming at when pulling the trigger. Other projectiles in the game (such as rockets, arrows, flares and syringes) are only limited by their reload rate.
 * I Wanna Be the Guy gives you four at a time. There's a glitch that takes this away in certain areas.
 * Glider PRO only allows two rubber bands to be on screen at once.
 * Some games allow you to raise the bar with an in-game powerup:
 * Jewel Master for example allowed you to raise different aspects of your spells (such as how many projectiles could be on-screen at once) by varying the levels of the rings that created them.
 * La-Mulana has a ring that gives an additional projectile on the screen.
 * Most Fighting Games, more often than not, allow a character only one projectile on the screen at once. There are exceptions aplenty, but for the most part, it's limited to one for the sake of game balance (to allow the other player ample opportunity to defend or counter).
 * One of the many annoying gameplay mechanics in Deadly Towers was having to attack with slow-moving throwing swords, of which only one could normally be on screen at a time. The Double Shot allowed you to have two swords on screen, and so did the Parallel Shot except they had to be fired at the same time.
 * In Metroid Prime, you can only have 3 missiles active at once. Normally their fire rate is so slow that this is completely irrelevant, but a an unintentional method of shooting them very quickly allows the limit to be reached.
 * In Metroid Fusion, you can only have three beam attacks, two missiles, and three bombs active on screen at once. The beam limit usually can't be noticed unless you are falling and firing down, so it rarely interferes with gameplay. The missile limit is also hardly noticeable in that, early on, you won't have many missiles, so you'll be firing each one carefully, rather than firing them rapidly and potentially wasting them. By the time you have more missiles to work with, your upgrades will have reduced the rate of fire of your missiles, making the limit much less noticeable.
 * Metroid II: Return of Samus had a limit of three beams, one missile, and three bombs on the screen at once. The beam limit is most noticeable when firing the Spazer or Plasma beams, since those actually consist of three beams fired at once (the Spazer fires them in a spread pattern, while the Plasma beam fires them in one line). If part of the Spazer hits an enemy but another part does not, often two of the beams will be out of sync with the third.
 * The Gradius series limits your ship you to two on-screen shots at a time, and the same goes for your Attack Drones. In Gradius V, however, this limit is extended to four shots.
 * Berzerk does this too. You can fire rapidly as long as it's point blank. (Do it against a wall up close for THE single most irritating sound you will ever hear in life.)
 * Space Invaders had a one-shot limit, but in the Atari 2600 version there was a trick to get two: Hold the RESET switch and turn on the game, then let it go. Double shots. Cheat or glitch? Nobody may ever know.
 * In Dissidia Final Fantasy, The Emperor's primary means of HP-destroying offense is Flare, an extremely large Painfully-Slow Projectile that makes up for it by strong homing and staying on the screen a very long time. There can only ever be two on the screen at once, presumably for reasons of game balance rather than technical limitations; if The Emperor could spam Flare, given its homing and duration, he could completely shut down the opponent with zero effort on the player's part.
 * Alive and well in all its Fake Difficulty in the Fun Orb game Star Cannon; in the second level, your bullets are the last priority for the game, after floating space debris and (sometimes undodgeable) enemy swarms. Your firepower is reduced to about 1/3 of normal...if you're lucky.
 * The shareware platform game Secret Agent also uses this. In fact, one of the power-ups is an upgrade which allows you to have two bullets at the screen at once.
 * The first Duke Nukem game (the 2D one) limited you to only one energy bolt onscreen at a time, upgradeable to four by way of powerups.
 * Genetos gives you two bullets at a time with the first ship (taken almost directly from Space Invaders), and five with the second (modeled after ships in late-eighties games), then abandons the trope as you move closer to the modern day.
 * In Captain Comic, the number of Blastola Cola 'bullets' you can have on the screen at once is limited to the number of cans you've picked up.
 * The Atari 2600 had specialized hardware for rendering "missile" sprites. It could only handle two missiles at a time, leading to the two-bullet limit of many 2600 games.