The Basics
 What is a chain?
It's just that, a chain. Think of a chain of events that leads to something, then apply the same principle to the Yu-Gi-Oh! Trading Card Game. Simply put, a chain is two or more cards played in response to something.
 How does a chain start?
Once someone activates a card effect, summons a monster, sets a spell or trap card, or declares an attack, the opposing player has the option to respond if he or she is capable of doing so. If the opponent responds, a chain is started. From that point forward, players may continue to go back and forth, responding to each other's cards, or in some cases responding to their own card, until neither player wishes to continue the chain.
 So... How does a chain work?
A chain works in reverse order of the way it starts. This means that the last card played in the chain is the first card to have its effect resolved. Let's look at a basic chain for an example:
Chain Link 4: Player B pays 1000 Life Points to activate Seven Tools of the Bandit. Chain Link 3: Player A activates Skill Drain. Chain Link 2: Dark Paladin's effect is activated and Player B discards a card from his/her hand. Chain Link 1: Player A activates Monster Reborn and targets Player B's Cyber End Dragon.
The move that starts a chain is always Chain Link 1. In this case, it was the activation of Monster Reborn. This chain also involves something called a **cost**, but that will be covered in a bit. In this example, Player B pays the cost of 1000 Life Points to activate Seven Tools of the Bandit to negate the activation of Player A's Skill Drain trap card, which was intended to negate the effect of Dark Paladin being able to negate and destroy a spell card at the cost of discarding one card from a player's hand. Since Skill Drain's activation was negated, Dark Paladin's effect is able to resolve, thus negating and destroying Player A's Monster Reborn. Chains can get much more involved than this by including multiple different effects that have to be resolved before the duel can continue, but we're not going to confuse you now.
 What is a cost?
A cost is just that: the cost of activating an effect. Costs must be paid before an effect is activated. Costs are also non-refundable, so once it's paid, it's paid. It doesn't matter if the card's effect and/or activation get negated; you don't get your Life Points or whatever you paid back. Costs can easily be a stumbling block for many new duelists, so be wary. Cards with costs should be used sparingly if you don't know what you're doing.
 Advanced Concepts
Occasionally, you'll run into a situation where multiple effects get activated in the same chain at the same time. These can get pretty tricky, especially when not everyone knows how they work.
 When multiple effects get activated at once on your side of the field...
You get to choose the order in which the effects resolve! For example, let's say that Player A activates Swords of Revealing Light when Player B has three face-down monsters. Player B flips all three monsters face-up, and two of them, Cyber Jar and Dice Jar, have a flip effect. Since Swords of Revealing Light doesn't stop flip effects from activating, Player B now has to determine the order in which the effects will resolve. By announcing Cyber Jar as Chain Link 1, Player B can activate Dice Jar's effect first and get the effects of both monsters, whereas by announcing Dice Jar as Chain Link 1, Cyber Jar's effect will resolve first and Dice Jar will no longer be on the field for its effect to be used. Use this to your advantage!
However, be warned that should the same thing happen to your opponent at the same time, he/she gets to do the same thing. **Plus**, if it's your turn, your opponent's effects will resolve before yours, so watch out!
 Spell Speeds
Spell speeds are the most important aspect of a chain. This determines whether a certain card can be activated during a certain step of the chain or not. There are three different levels, with each one "faster" than the level below it.
 Spell speed 1
The slowest of spell speeds, spell speed 1 is reserved for normal, equip, and field spell cards. Because these cards are so slow, you may only activate them on your turn. Because of this, you can also set a spell speed 1 card in your spell/trap card zone and activate it later in that turn during either of your [[[Main Phase]]s if you like. Note that spell speed 1 cards cannot be used against each other in a chain. Only spell speed 2 or 3 cards may be used against them
 Spell speed 2
The next fastest of spell speeds, spell speed 2 encompasses normal and continuous traps, and quick-play spell cards. These cards are generally the second or third step in a chain and can be used against each other. However, these types of cards have special rules as to how they may be played.
 Normal/Continuous traps
As these are just that, traps, you can't play them face up on the same turn you get them. You must first set a trap face-down in your spell/trap card zone and wait until your opponent's Draw Phase before you can activate it.
 Quick-Play spells
Because of how these cards may be played, one may think that they should belong in spell speed 3, but alas, they don't. Quick-play spell card may be played from your hand at any point during your turn when there is a situation that you may use a spell speed 2 card or you may set it face-down in the proper zone. However, by doing so you cannot activate a quick-play spell on the same turn you set it unlike spell cards in the spell speed 1 group; you must wait until your opponent's next Draw Phase.
 Spell speed 3
The fastest of all spell speeds, spell speed 3 cards cannot be chained to by anything slower than another spell speed 3 card, but may be used at any point within a chain. Because it's the fastest spell speed, only counter traps belong to this group.
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