Editing Controlled loop

A '''controlled loop''' is a series of voluntary actions that can be repeated as many times as a player wants. There is no uncontrollable element to these loops and a player can choose to stop them at any time, so they are legal to use.

Some loops that require only a few cards (fewer than 4) to pull off have caused cards to become [[Forbidden]] or [[Limited]] on the current Forbidden/Limited lists, as otherwise their presence would be detrimental to gameplay.

They contrast to [[infinite loop]]s, which the players have no control over once they start.

==Examples==
===Quillbolt Loop===
{{main|Quillbolt Loop}}
This uses the effect "[[Quillbolt Hedgehog]]" to [[Special Summon]] itself by having a [[Tuner monster|Tuner]] on the field along with a monster effect that Tributes a monster for damage such as "[[Cannon Soldier]]". "Quillbolt" can be Tributed again and again and continuously revived, as long as "[[Imperial Iron Wall]]" prevents "Quillbolt Hedgehog" from being [[banish]]ed by its own effect.

A far more consistent variation of this loop uses "[[Plaguespreader Zombie]]". Summon both "Quillbolt" and "Plaguespreader" to the field, and Xyz Summon "[[Ghostrick Socuteboss]]", then activate its effect. Then, Summon "[[Ghostrick Angel of Mischief]]" by using "Socuteboss" as the Xyz Material", then detach an Xyz Material (not "Socuteboss") to add a generic "Ghostrick" Spell/Trap to your hand. Place this Spell/Trap back on top of your Deck to revive "Plaguespreader", then revive "Quillbolt" with its effect. This returns to the start of the loop.

===Flint Lock Loop===
{{main|Flint Lock Loop}}
This uses "[[Flint]]" and two "[[Flint Lock]]s" to pass the "Flint" back and forth. The [[Spell Card]] "[[Morale Boost]]" is used to gain 1000 [[Life Points]] every time an [[Equip Card]] is equipped. Because no Equip Card leaves the field, the effect to lose 1000 Life Point is never reached. This allows a player to gain an unlimited number of Life Points while the opponent may be powerless to stop it.

===Gearfried Loop===
If a player controls "[[Gearfried the Iron Knight]]", then it is possible to activate "[[Butterfly Dagger - Elma]]" an unlimited number of times per turn, by [[equip]]ping it to "Gearfried", whose effect will [[destroy]] it, at which point "Elma's" effect will return it to the hand to be equipped again. This can easily be combined with "[[Royal Magical Library]]" to draw an unlimited number of cards in one turn (causing an easy [[Exodia]] [[FTK]], etc.). Another option is to combine it with "[[Spell Absorption]]" to gain an arbitrarily high number of [[Life Points]]; adding "[[Fire Princess]]" gives an unlimited amount of damage to inflict in one turn on top of that. This loop is the reason why "Butterfly Dagger - Elma" is currently [[Forbidden]] on the Forbidden/Limited List.

===Gate Material Loop===
By combining "[[Fusion Gate]]" and "[[Chain Material]]", it is possible to Summon or activate nearly any card an unlimited number of times per turn, through the correct (and very risky) setup. These loops generally revolve around Fusion Summoning several [[Fusion Monster]]s by [[banish]]ing [[Fusion Material Monster]]s from the [[Main Deck]], followed by using said monsters to activate effects or Summon other monsters, then finally Fusion Summoning "[[Elemental HERO Electrum]]" to return the originally banished monsters back to the Deck to be banished again. For an example, see [[Elemental HERO Gustav Max OTK]], an [[OTK]] that involves Summoning "[[Superdreadnought Rail Cannon Gustav Max]]" at least four times in one turn. For further and more detailed examples of possible setups, see [http://forum.duelingnetwork.com/index.php?/topic/99712-gate-material-decks-the-ultimate-comprehensive-guide/#entry1652884 this external link].

===Primal Seed Loop===
If a card is active that banishes Spell Cards that would go to the Graveyard (such as "[[Macro Cosmos]]" or "[[Winged Kuriboh LV9]]"), and there is a "[[Black Luster Soldier - Envoy of the Beginning]]" or "[[Chaos Emperor Dragon - Envoy of the End]]" on the field, then any player with two copies of "[[Primal Seed]]" and a [[Normal Spell Card|Normal]] or [[Quick-Play Spell Card]] in their hand can activate that Spell Card an unlimited number of times per turn, by repeatedly using one copy of "Primal Seed" to bring back the other copy along with that Spell Card. This allows for an [[OTK]] with a card as weak as "[[Sparks]]", as well as numerous other possibilities such as arbitrarily high Life Points or ATK. This loop is why "Primal Seed" is currently [[Limited]] in the ''OCG''; it was Limited in the ''TCG'' as well until [[April 2014 Lists (TCG)|1 April 2014]].

===Wicked Worm Beast Loop===
If "[[Wicked Worm Beast]]" is Special Summoned in the [[End Phase]] of the turn it is automatically returned to the hand. Therefore, if a player has 7 or more cards in their hand in the End Phase of the turn and "[[Dark World Grimoire]]" active, they can discard "Wicked Worm Beast", Special Summon it with "Grimoire", and return it to the hand again. Although this has limited value, if the opponent activated "[[Maxx "C"]]", they could Deck out. Similar strategies can occur using "[[DNA Surgery]]" and "[[Cyber Summon Blaster]]" or "[[Soul-Absorbing Bone Tower]]", the latter of which works with "[[Zombie World]]". This loop is more easily achieved using "[[Silent Wobby]]" with a card that takes control of it.

===ABC Loop===
This loop uses two copies of "[[A-Assault Core]]" and "[[Firewall Dragon]]". When "A-Assault Core" is sent from the field to the [[GY]], its effect can be activated in order to add the second "A-Assault Core" from the GY to the hand, while also triggering the effect of "Firewall Dragon" as Chain Link 1, allowing the player to Special Summon "A-Assault Core". This can be abused by using "[[Cannon Soldier]]" in order to Tribute "A-Assault Core" every time it is Summoned, inflicting as much damage as needed in order to win. In order for it to work, the player must have at least one other monster in their hand that can be Special Summoned by "Firewall Dragon", otherwise its effect cannot be activated.

This strategy was adopted by some ''[[OCG]]'' players during the April 2018 format for being easy to pull off, but also because they were able to play normally even if the FTK was stopped.<ref name="abc loop">[https://roadoftheking.com/ocg-2018-04-metagame-report-9-10/ Road of the King] - OCG 2018.04 Metagame Report #9, #10</ref> The combo is no longer possible due to the 2021 errata of "Firewall Dragon" restricting its effects to only being able to be used once per turn.

===Samsara Lotus Loop===
"[[Samsara Lotus]]" can Special Summon itself from the GY during the End Phase as long as the player does not control any Spell/Trap Cards. This can be combined with three other cards: "[[Topologic Bomber Dragon]]", "[[Knightmare Cerberus]]", and "[[Trickstar Black Catbat]]". "Topologic Bomber Dragon" must be in the [[Extra Monster Zone]], while "Knightmare Cerberus" is [[co-link]]ed with "Trickstar Black Catbat". By Special Summoning "Samsara Lotus" to the zone pointed to by "Black Catbat", the effect of "Topologic Bomber Dragon" is triggered, destroy all monsters in the [[Main Monster Zone]]s. Since "Cerberus" and "Black Catbat" are co-linked, neither of them are destroyed because of the effect of "Cerberus", and only "Samsara Lotus" is destroyed. When that happens, the effect of "Black Catbat" inflicts 200 damage to the opponent. This can be repeated any number of times, since none of these cards have restrictions to how many times they can be used.

Despite requiring this many monsters on the field, there are several ways to perform this with 1 or 2-card combos by Summoning monsters like "[[Aromaseraphy Jasmine]]", "[[Crystron Halqifibrax]]" and "[[Summon Sorceress]]".

===Telefon Loop===
"[[Morphtronic Telefon]]" has an effect to Special Summon a "[[Morphtronic]]" monster from the GY whose its [[Level]] were equal or lower than the [[Dice|dice]] roll result of this effect. Due to this effect is only a soft [[once per turn]] and the fact that "Telefon" can summon another copy of itself regardless of the dice roll result due to being a [[Level 1 Monster Cards|Level 1 monster]], player can infinitely Special Summon each copies of "Telefon" back-and-forth from their GY as long as they were not interruped by opponent's card effects. This can be exploited by either using each copies of "Telefon" to conduct any number of [[Link Summon]]ing as long as the user wished, as well as being used as an infinite fodder for a tribute-burn cards such as "[[Cannon Soldier]]".

==Tournament rulings==
Current tournament rules state that if a player wants to perform a controlled loop, they may physically perform the loop once and then tell their opponent exactly the number of times they wish to repeat it. The opponent may then respond to any iteration of the loop by stating the iteration number.<ref>[https://web.archive.org/web/20201118000152/https://img.yugioh-card.com/en/gameplay/penalty_guide/YGOTCG_Policy_v_2_1.pdf]</ref>

For example:
* Player 1 controls "[[Imperial Iron Wall]]", "[[Glow-Up Bulb]]", "[[Cannon Soldier]]", and "[[Quillbolt Hedgehog]]".
* Player 1 Tributes "Quillbolt Hedgehog" for the effect of "Cannon Soldier" to inflict 500 damage. Player 2 does not respond.
* Player 1 Special Summons "Quillbolt Hedgehog" with its own effect. Player 2 does not respond.
* At this point, Player 1 may tell Player 2 that they intend to repeat the loop a total of 16 times / 15 more times until Player 2's LP are reduced to 0. Player 1 does not need to physically move cards 15 more times.
* Player 2 may respond by stating they intend to Chain "[[Hope for Escape]]" on exactly the 12th time "Quillbolt Hedgehog" activates its effect.
* "Hope for Escape" resolves (or Player 1 responds to "Hope for Escape" and that Chain resolves).
* The controlled loop is considered to end here. If Player 1 wants to continue the loop at this point, they must physically move cards to Tribute and Special Summon "Quillbolt Hedgehog" 1 more time, giving Player 2 an opportunity to respond before Player 1 may declare another controlled loop.

==In the anime==
* In {{episode|gx|64|ref}}, [[Syrus Truesdale|Syrus]] used the mandatory effect of [[Tyranno Hassleberry|Hassleberry]]'s "[[Ultimate Tyranno (anime)|Ultimate Tyranno]]" against him, forcing it to attack and destroy "[[Decoyroid (anime)|Decoyroid]]" over and over while the combined effects of "[[Ambulanceroid (anime)|Ambulanceroid]]" and "[[Rescueroid (anime)|Rescueroid]]" continuously Summoned it back to the field. This allowed Syrus's "[[Cyber Summon Blaster (anime)|Cyber Summon Blaster]]" to continuously damage Hassleberry until he lost the Duel.
* In {{episode|zexal|98|ref}}, [[Yuma Tsukumo]] and [[Astral]] fused into [[Dark ZEXAL]] against [[Vector]], with the latter, who was blinded by rage, taking control. He equipped "[[DZW - Chimera Clad (anime)|Dark ZEXAL Weapon - Chimera Clad]]" to "[[Number C39: Utopia Ray V (anime)|Chaos Number 39: Utopia Ray V]]", granting it immunity by battle destruction and the ability to [[attack]] once again with doubled [[ATK]] whenever Dark ZEXAL took [[battle damage]] from attacks involving it. He then proceed to attack the higher-ATK "[[Number 104: Masquerade (anime)|Number 104: Masquerade]]", taking the first damage and triggering the first ATK boost. However, Vector [[activate]]d "[[Extra Hundred]]" in response to the second attack, preventing "Masquerade" from being destroyed in exchange for letting "Utopia Ray V" attack it a third time. However, by the second effect of "Extra Hundred", each time "Masquerade" would be targeted for an attack from then on, its ATK would become 100 points higher than the attacker's. Astral didn't realize the danger, and continued to attack with "Utopia Ray V" again and again, losing 100 [[LP]] each time, until he was down to 600. At that point, Yuma managed to cancel the fusion and promptly ended the turn, preventing the 500 damage of "[[Sargasso the Different Dimension Battlefield (anime)|Sargasso the Different Dimension Battlefield]]" from reducing their LP to 0. Had he not managed to, Astral would probably have continued the loop until he lost.
* In {{episode|arcv|61|ref}}, [[Yuya Sakaki|Yuya's]] opponent, [[Chojiro Tokumatsu]] had "[[Flower Cardian Lightshower (anime)|Flower Cardian Lightshower]]" on the field, making it that every time Yuya drew a card, he would take 1500 damage, so long as Chojiro skipped his Draw Phase. Chojiro also had "[[Fraud Freeze (anime)|Fraud Freeze]]", preventing Yuya from performing a Pendulum Summon on his turn. When Yuya had 1000 Life Points remaining and his next draw would result in defeat, Yuya drew "[[Performapal Rain Goat (anime)|Performapal Rain Goat]]", an effect he immediately activated, discarding it to reduce the 1500 damage from the effect of "Lightshower" to 0. Yuya then activated the effect of "[[Performapal Teeter Totter Hopper (anime)|Performapal Teeter Totter Hopper]]" from his Graveyard, because a monster was sent from the hand to the Graveyard. Furthermore, when Summoned by this effect, "Teeter Totter Hopper" cannot be destroyed by battle once per turn, but during the End Phase of the opponent's turn, it can be sent to the Graveyard to add a Level 3 or lower "Performapal" monster from the Graveyard to the hand. Yuya would use this effect to add "Rain Goat" back to his hand every turn, thus preventing Chojiro from inflicting damage with "Lightshower", and "Lightshower" won't be able to destroy "Teeter Totter Hopper" due to its effect, creating a loop that can only be broken if Chojiro draws a card, which he did so on his next turn. Had he continued on without drawing, he would have had to continue the loop for an extensive amount of time for Yuya to run out of cards from his Deck, but at the same time, would have given Yuya a major hand advantage that could have resulted in his defeat. 
* In {{episode|arcv|99|ref}}, [[Declan Akaba]] activated the effect of "[[D/D/D Chaos King Apocalypse (anime)|D/D/D Chaos King Apocalypse]]" against [[Jean-Michel Roget]], which lets him Special Summon it from his hand by destroying two face-up Spell/Trap Cards he controls, those cards being "[[D/D Savant Nikola (anime)|D/D Savant Nikola]]" and "[[D/D Savant Thomas (anime)|D/D Savant Thomas]]". Since "Nikola" was destroyed while it was in the Pendulum Zone, its effect let Declan return a "D/D/D" monster, "Chaos Apocalypse", on his field to his hand, and then place up to two face-up "D/D" Pendulum Monsters from his Extra Deck ("Nikola" and "Thomas") to his Pendulum Zone. Declan followed up with "[[Dark Contract with the Swinging Abyss]]", which inflicted damage to the opponent equal to the DEF of a "D/D" Pendulum Monster that was returned to his hand. As the DEF of "Chaos Apocalypse" is 2000, this was enough to wipe out the rest of Jean's LP. Attempting to bypass his loss, Jean re-entered the Duel and took the 2000 LP intrusion penalty. Declan revealed that he would simply use the effect of "Chaos Apocalypse" to Special Summon it again, triggering the effect of "Nikola", and in turn triggering the effect of "Abyss Pendulum", which would deplete Jean's LP again. Realizing that Declan would repeat this loop each time he attempted to re-enter the Duel, Jean forfeited and fled.
* In {{episode|arcv|133|ref}} of ''ARC-V'', [[Yuri]] activated the Ignition Effect of "[[Starving Venom Fusion Dragon (anime)|Starving Venom Fusion Dragon]]" targeting [[Yusho Sakaki]]'s "[[Performapal Sky Magician]]" to gain its effects. However, he then chained the effect of "[[Clear Wing Synchro Dragon (anime)|Clear Wing Synchro Dragon]]", destroying "Starving Venom" and gaining its ATK. Yuri proceeded to activate "[[Destruction Flower]]" and "[[Destruction Fruit]]", with the latter reducing the ATK of "Clear Wing" by 3000 to Summon back "Starving Venom", and the former inflicting damage to Yusho, and reducing the ATK of "Sky Magician", equal to difference between current and original ATK of "Clear Wing", initially 200. As "Starving Venom" was just Summoned again, Yuri triggered the combo by activating its Ignition Effect again. The loop was repeated a total of 5 times, with the damage increasing by 200 points each time, until the ATK of "Sky Magician" dropped to 0 and Yusho's LP to 200, meaning that repeating once more would have caused his loss. However, Yuri instead had "Starving Venom" attack "Sky Magician", defeating Yusho by battle damage.
* In the ''[[Yu-Gi-Oh! The Dark Side of Dimensions]]'' film, in response to [[Aigami]] targeting [[Yugi Mutou (manga)|Yugi's]] "[[Lord Gaia the Fierce Knight (anime)|Lord Gaia the Fierce Knight]]" for an attack with his "[[Indiora Doom Volt the Cubic Emperor (anime)|Indiora Doom Volt the Cubic Emperor]]", the latter activated his Set "[[Dimension Sphinx (anime)|Dimension Sphinx]]", targeting "Lord Gaia", inflicting damage to Aigami equal to the difference between the ATK of "Lord Gaia" and a monster that attacked it, provided the attacking monster's ATK was at least double the ATK of "Lord Gaia". Yugi then activated his Set "[[Dimension Guardian (anime)|Dimension Guardian]]" and targeted "Lord Gaia", preventing its destruction by battle while it remained in Attack Position. Finally, Yugi activated his Set "[[Dimension Mirage (anime)|Dimension Mirage]]", and targeted "Indiora Doom Volt", allowing Yugi to banish monsters from his Graveyard to force it to declare another attack so long as it failed destroy a monster Yugi controlled by battle. As "Lord Gaia" was being attacked by "Indiora Doom Volt", a monster with more than twice its ATK, the effect of "Dimension Sphinx" inflicted damage to Aigami equal to the difference between the battling monsters' ATK. Due to the effect of "Dimension Guardian", "Lord Gaia" was not destroyed by that battle, allowing Yugi to activate the effect of "Dimension Mirage", banishing a monster from his Graveyard to force "Indiora Doom Volt" to attack "Lord Gaia" again, once again triggering the effect of "Dimension Sphinx". Yugi then repeated this loop by banishing monsters for the effect of "Dimension Mirage" until he depleted Aigami's LP.
* In {{episode|vrains|102|ref}}, [[Yusaku Fujiki|Playmaker]] attacked [[Bohman]]'s "[[Perfectron Hydradrive Dragon]]", whose effect prevents battle damage as long as it has [[Hydradrive Counter]]s and allows it to protect itself from battle destruction by removing 1 of them (which he had 4 of at that point), with "[[Firewall Dragon Darkfluid (anime)|Firewall Dragon Darkfluid]]". After [[damage calculation]], a mandatory effect of "Perfectron" activates which would destroy all monsters Playmaker controls, but "Darkfluid" negated it using one of its own counters (of which it also had 4). The effect of "Darkfluid" also allows it to attack again if it negates an effect while battling, so Playmaker repeatedly attacked "Perfectron" until its counters ran out and Bohman took damage, which was enough to drop his LP to 0.

== References ==
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