Knockback

"Any outdoorsman will tell you the most frustrating part of hunting is when a deer simply FALLS DOWN when shot, and doesn't FLY BACKWARDS into the forest."

- Team Fortress 2 advertisement of a weapon with high knockback

The first and foremost reason why players hate those Goddamned Bats, and the means by which many Ledge Bats send players plummeting to their doom....

Knockback is a Video Game simplification of basic physics where if a character is struck by an attack, it will physically push them aside some measure of distance. Modern games featuring full physics engines can incorporate numerous factors (relative mass, speed, gravity/wind, etc.) to calculate the exact force and direction of it, while older and simpler (and by extension, Retraux) will use extremely simplified rules, such as whether the attack originated from the right or left of the player.

But regardless of its technical implementation, its actual effect on gameplay can be sorted into rough categories:


 * Flinching: Short-term knockback yields little more than a 'flinching' animation and may interrupt whatever action the player was performing (a combo or Charged Attack, say). The knockback otherwise does not impede or interfere with player movement or control.
 * Knocked back: The most common manifestation of knockback interrupts the player's action and momentum and pushes them back a short distance (perhaps one or two steps); the character recovers their footing quickly, and the player is able to resume action in short order.
 * Knocked down: In its extreme manifestation, the player's character may be knocked back a significant distance, and the player is unable to control them until the character comes to a stop and is able to get back up onto their feet again.

In all three cases, knockback is usually accompanied by some measure of Mercy Invincibility so that the player doesn't have to worry about becoming "stunlocked", trapped in a Cycle of Hurting where the next hit lands faster than the character can recover from the previous.

Knockback can also be used strategically, as a weapon of its own: A player on the losing end of a Fighting Game may be able to trigger a surprise victory by knocking their opponent out-of-bounds, and (by extension) the Ring Out Boss lives or dies by who gets knocked outside the arena first. A Get Back Here Boss may defend himself by knocking the player out of their attack range, and on the other hand a player can scatter a Zerg Rush with it, to engage and defeat foes individually. And then there's the Good Bad Bug known as the Rocket Jump, exploiting the knockback of an explosive weapon to send the user airborne.

Of course, some enemies won't suffer any knockback (or even flinch) when struck by the player's attacks -- for Bosses, which are typically larger than the player already, this may be considered a standard part of their Contractual Boss Immunity. Likewise, players may sometimes be given this advantage via a Status Buff (or as a property of certain moves), and sometimes it is the only way to survive That One Attack. In Fighting Games, being immune to knockback is sometimes referred to as having "Super Armor".

And speaking of strategic uses, knockback is all-too-often remembered for occuring during precision maneuvers, such as when making timed jumps across Floating Platforms; every videogame character has at some point been sent plummeting into Spikes of Doom, or down the nearest Bottomless Pit due to taking a hit at the wrong moment; it's the culprit for many a Game Over screen (as well as a few broken controllers).

If the player has a command to parry or block enemy attacks, this may reduce or eliminate the knockback associated with it (or it will result in a Knockback Slide, with the character still on their feet). However, defending also tends to block the Mercy Invincibility, which can become a danger of its own if the attack still inflicts Scratch Damage, or has the potential to overpower ("guard break") the character's defense.

If the protagonist is a One-Hit-Point Wonder then knockback is rarely a concern (except for some of the aforementioned uses), but may still occur if the hit cost the player their current powerup of their current life.

See also the Law of Inverse Recoil, and for extreme cases, Blown Across the Room and its melee counterpart, Punched Across the Room.

Note: Because of its ubiquity in Video Games, please limit examples to strategic uses or unusual occurrences.

First-Person Shooter

 * As mentioned, Rocket Jumping is a common technique exploiting the blasts from explosive weapons.
 * Golden Eye 1997 and Perfect Dark have a knock back for the player if they get shot. This also stops the player from shooting for a brief second. Combine this with several enemy soldiers and you're bound to lose more than half your health while unable to to fire back. Luckily, the enemy AI is programmed to stop firing for a moment and then resume.
 * The Medal of Honor games also have hit-stun. If an enemy catches you off-guard at close range with an automatic weapon on Hard difficulty, you may be stunlocked. Conversely, due to the use of Hit Scan, the knockback doesn't affect the enemy's aim, so they can continue shooting at you while apparently flinching. The snipers in Allied Assault not only deal the most damage and knockback of all mooks, but they also fire at a higher rate than the rifle infantrymen.
 * Shotgun Z-Secs and Pinky Demons in Doom 3 both deliverable sizable knockback, the former bordering on Blown Across the Room, and can result in Stun Lock.
 * In Team Fortress 2 regular attacks have an amount of knockback generally proportional to damage and only something like the Heavy's minigun does enough damage for this knockback to impede movement instead of just messing with aim. There are some special cases which do much more: explosives, the Scout's Force-A-Nature, sentry guns (which can be even harder to deal with than its damage, especially since the default Ubercharge does not protect against knockback), melee Critical Hits, and the Pyro's airblast (which does nothing but knockback). Probably the most bizarre thing is that damage over time (fire, bleeding) causes upward knockback for the sake of messing with the user's aim. The Soldier's Mantreads and the Quick-Fix's Ubercharge, respectively, reduce 3/4 and all knockback from sources that also inflict damage (i.e. everything but airblasts).

Platform Game

 * La-Mulana utilized significant knockback. Touch even the slightest enemy or brush up against a spike and Lemeza is sent sailing across the room at full velocity, with no ability to alter his trajectory until he lands.
 * In the sidescrolling Mega Man titles, knockback always occured relative to the direction Mega Man was facing, regardless of the direction of attack. In the "classic" series, it also interrupted charged Mega Buster shots (starting in 5, 4's Mega Buster was more stable), and in 9, Proto Man suffered double the knockback of Mega Man.
 * The sidescrolling Super Mario Bros. games generally provided Mercy Invincibility without knockback, which allowed players to short-circuit the fights with Bowser simply by running through him and grabbing the axe at the far end of the arena. This was changed in New Super Mario Bros, where coming in direct contact with Bowser knocks Mario back, away from the switch at the opposite end of the arena.
 * In the Wonder Boy series (as well as its many ports), Mercy Invincibility only protected the player from further HP loss; it did not protect the player from being knocked back or juggled by repeated attacks.
 * The rocks in the first game, which were the only non One-Hit Kill hazard, tripped Wonderboy when he ran into one, potentially bouncing him into an enemy or Bottomless Pit.
 * Castlevania. :cough: Medusa Heads :cough: Bottomless Pits :cough:.
 * Castlevania: Portrait of Ruin has an equip that negates your character's stun animation (and by extension, knockback), but with it equipped, you may not notice that you're taking damage until it's too late.
 * Castlevania: Symphony of the Night has two distinct types of knockback. Usually, taking damage just shoves Alucard back a couple of steps, but if he takes one hit that depletes half or more of his maximum HP, he goes flying and won't stop until he hits a wall, at which point he briefly sticks to it before falling down. In the special Luck Mode, this severe knockback is what lets you skip the screen where Death steals Alucard's equipment thanks to his greatly lowered stats: in normal gameplay, the only time you're likely to see it happen is if Galamoth hits you with one of his more damaging attacks.
 * The first Flintstones NES game made the player fall back and be stunned for a second when hit, often down the pit. The second game removed the knockback, although the stun effect remained.
 * The protagonist in Cave Story receives knockback only based on the direction he was hit from. This is an interesting case because while the character receives knockback, you're still in full control, enabling you to affect the distance of the knockback to a certain degree. In fact, the character rarely gets knocked back, but often forward or forward and up. Furthermore, abusing vertical knockback from crashing into a flying enemy is the only way to get a certain item without backtracking (or grabbing the Machine Gun).
 * The large knockback in the original MSX Valis, combined with the lack of Mercy Invincibility, frequently caused Yuko to be stunlocked and juggled to death.
 * The NES Ninja Gaiden trilogy. Like Mega Man, it always occurs opposite the direction you're facing. This can be a problem if constantly assaulted by Goddamned Bats during a platforming sequence.

Fighting Game

 * Many fighting games feature "grapple" and "throw" moves, and knocking an opponent out-of-bounds can trigger a Ring Out in various titles.
 * Some fighting games like Guilty Gear have a pushblock mechanic that allows a defender to enter a state where the opponent is pushed away when their physical attack is blocked.
 * The Super Smash Bros series is based entirely around Ring Outs; characters do not have depletable HP but instead receive greater knockback as they take damage, until they are inevitably thrown from the arena.
 * Some games such as later King of Fighters entries take Knockback to an extreme, making some attacks capable of bouncing an opponent off the wall/floor in order to extend combos.
 * A key game mechanic in Dissidia Final Fantasy, in the form of Wall/Floor/Ceiling Rush. Essentially--many attacks send the opponent away from the fighter at high velocity. If an attack has the ability to wall rush, and there's a wall somewhere along the victim's trajectory, they'll slam into it for extra damage (base value of one-half of the damage done by the original hit in Dissidia, one-quarter in Duodecim). Interestingly, various attacks have various 'likelihoods' of wall rush--a lot have zero chance of rushing, no matter if your opponent is right up next to the wall/ceiling, some have wall rush for a certain amount of distance (e.g. Bitter End can wall rush, but the opponent recovers if there's no wall for a long way), and a very amusing few (Nightglow, Shadow Bringer, and Cross Slash, for few) basically have guaranteed wall rush--so long as there is a surface to slam into, the opponent will do it--even if the closest wall is hundreds and hundreds of meters away.
 * In fact, Cloud's fighting style is aggressively dependent on Wall Rushing. Almost all of his skills have a high chance of Wall Rush, and his most basic attacks will generally send the opponent flying into a wall (or enable a chase scene, if the wall is too far away). Abusing this mechanic is his raison d'etre: he's not just hitting you hard, he's hitting you hard, then slamming you into a wall for more damage while he rushes after you to rinse and repeat.

Action Adventure

 * The Legend of Zelda has various enemies whose main power is having more knockback than most, and the Oracle games featured a ring that reduced knockback.
 * The final segment of the Final Boss of Beyond Good and Evil suddenly ramps up the effects of the game's knockback--while present-but-negilible before, even a small attack will now result in the heroine getting totally decked. During one sequence of attacks, it is entirely possible to get "stunlocked" and make the fight Unwinnable until you inevitably die and get sent back to the checkpoint.
 * Deadly Towers has Prince Myer get knocked in whatever direction is opposite the way he's facing quite a distance without a way to stop himself. Unfortunately, this game also features Bottomless Pits...

Real Time Strategy

 * While Warcraft III doesn't feature knockback, the trope's omnipresence is such that it's a very rare (custom) map that doesn't have this mechanism (such as Defense of the Ancients and its variants).
 * Dawn of War has knockback for artillery and some units. Justified for some (Super Strength, Psychic Powers, etc), but it does get a bit ridiculous when the Kroot (lanky hollow-boned bird-men) are upgraded to knockback units such as seven-foot-tall Power Armored Space Marines with the same ease as ordinary Guardsmen and Gretchin. Also a fallen unit ordered to move will do so while playing their "get up" animation, so they end up gliding majestically along the ground before getting up.
 * Myth 1 and 2 have a flinch mechanic that is fairly central to gameplay as it allows certain rock-paper-scissors balancing. For example, the fast but unarmored Berserks can often kill heavily armored Warriors by whaling on them fast enough that the Warrior can't get a swing in from all the flinching. However, the same Berserks have a tough time against archers, as being hit causes the Berserk to stop running while he flinches--making him an easier target. Those heavily-armored Warriors are less likely to take damage from arrows, and still less likely to take enough to flinch.

MMORPG

 * World of Warcraft featured knockbacks by various NPC mobs and bosses from when the game was first released, but players didn't get access to them until Patch 3.0, the Wrath of the Lich King expansion, when a small handful of abilities were given to various classes that would knock NPCs or other players back. NPCs don't take falling damage and can run up some sheer cliffs so Knockback abilities are generally underpowered against them, but in certain limited circumstances Knockback effects can be very, very powerful in PvP.
 * Humorously, they can get so annoying in dungeons (they disrupt positioning and can knock enemies into reinforcements) that several classes have the ability to turn off the knockback aspect of the spell through the use of a glyph (Mages, Druids, and Shaman, for those who care.)
 * The flinching ability is available from the start however, in the form of various stuns as well as interrupts.
 * City of Heroes has three versions: knock back, knock up, and knock down. Almost all melee classes have a power that resists these effects. There also exist enhancements that provide the player with resistance to it, which are in very high demand as most players hate being knocked around by enemies. There also exist enhancements for increasing the knockback in your own powers.
 * As an action MMO, Dragon Nest practically requires players to exploit the various forms of this trope as even Mooks can easily do the same. Resistance to this trope can be a Game Breaker especially in PVP.
 * Star Wars: The Old Republic has it in various forms. From the simple 'interrupt' ability that interrupts abilities being cast or channeled (and preventing it from being cast again in a few seconds), then there are 'stun' and knock down abilities that is as good as it sounds (but also on very long cooldown), to knockback abilities that sends the enemies flying.

Third-Person Shooter

 * Gears of War 2 and 3 implement a "stopping power" system where being shot slows the player's movement toward the shooter. This was added to prevent players from charging through a hail of machine gun fire for a close-quarters execution with a shotgun. In addition, smoke grenades in 3 (and post-patch 2) cause a flinch effect, while in 1 and pre-patch 2 cause full-on knockback, though they deal no actual damage in either case.

Turn-Based Strategy

 * Hoshigami has an entire game mechanic centered around knocking enemies into a chain of allies to incur massive damage and have a chance at stealing an item, but unfortunately setting up such a chain leaves your party very vulnerable so it's only useful for eliminating the last enemy on a map.

Role Playing Game

 * In Mass Effect 2 when your character is hit by "impact" attacks (Explosive or telekinetic powers) he or she will stumble and move back a step or two. This is completely logical given that they are being hit by a physical force, but this effect is rather Egregious when your character is hit while ducking behind cover. In this case, when you are already crouched down on the ground, your character will stand up before they stumble and take a step back. This means your character is deliberately moving out of cover, since they take an independent action (standing up) before they are uncontrollably knocked back by the force, instead of simply falling down or stumbling where they were.
 * The Elder Scrolls: Oblivion has an effect that may apply to power attacks called "knockback". Mechanics-wise, this is more like "go completely limp" where you then have to struggle to your feet and hope the enemy doesn't pull one off again.
 * In Skyrim, a power attack will cause an opponent to stagger, and the Unrelenting Force shout will stagger an enemy, or send them flying at it's highest level.
 * One of the higher tier archery abilities, Power Draw, introduces knockback to arrows, half the time. Needless to say, the ability to stun an opponent at range over and over again is almost a Game Breaker. The only reason it isn't is because it only affects creatures that are about as big as the player; dragons, for example, don't care about knockback at all.
 * In Diablo II, knockback is a specific effect that can be either part of an attack, or a modifier on a weapon. Knockback is guaranteed to make an enemy flinch and interrupt their attack, but it may take longer to kill enemies in melee because you'll have to keep walking up to them.
 * In Xenoblade Chronicles, enemies are susceptible to fall damage, so the well-timed use of attacks with knockback on them can shove them off cliffs for an instant kill. Coupled with moves that induce the sleep status (Which are both difficult to dodge, and reduce the affected enemy's evasion to zero), this can allow you to kill enemies that are much higher leveled then you, and reap the overpowered rewards from it. For this reason, bosses are completely immune to knockback. Of course, enemies are also just as capable of doing the same thing to you, and with greater ease, as while your attacks only shove them back a few body lengths, their attacks can send the party flying about five times as far, with the added annoyance of almost always causing you to be dazed from the landing.
 * Also present in the game is the Topple status, which knocks the victim off their feet, and makes them completely unable to act or avoid attacks. It's essential to defeating some early bosses that can't be hurt while standing on their feet, and also turns into a bit of a Game Breaker later on, as topple inducing attacks can potentially be chained together to the point where the enemy can never get up until they're dead.

Other

 * Dwarf Fortress has knockback as a possible effect of blunt attacks, launching the enemy a short distance calculated according to a staggering number of different variables. In previous versions this was insanely but hilariously overpowered, with even fairly unremarkable warriors able to launch opponents six or seven tiles. The recent combat mechanics overhaul makes knockback possible with all weapons, now that slashing or piercing attacks are re-rolled as bludgeoning ones if they fail to overcome the target's armour check, but for better or worse it also severely nerfed it.