Yu-Gi-Oh! Solitaire (or, as my kid brother likes to call it, AUTO-OPPONENT BLAST!)

For a while now, I've been considering how one would create a Yu-Gi-Oh! solitaire format. After some inspiration from a Magic: The Gathering multiplayer format (here, if you're curious) and some experimenting, I've come up with a basic structure that I think makes for a robust single-player game. Note that this format probably won't be helpful in improving your gameplay against a living opponent; there are no allowances for bluffing, metagaming, or other psychological aspects. The (imaginary) opponent is rock-dumb by necessity; it can't "reason," but instead relies on a set of "instincts" (rules) that I have provided. Feel free to experiment with your own variations (and even to share).

One key to a format of this nature is that it should be intuitive; I've tried to make this as much so as possible. I've helped my kid brother (who is 10) play it a few times, and he seems to have picked up on the basics pretty quickly. (At any rate, he always realizes right away when the opponent is likely to have a big turn.) Something that amazes me a bit about the format is that many of the cards that feel like well-balanced cards for it are actually some of the worst cards in the game. (If you want a sampling, either of cards I've actually put into the experimental version of the deck or cards I think potentially would work [possibly, in fringe cases, with additional rule suggestions], ask in the comments.)

The key here, of course, is to have fun, especially with cards that you wouldn't necessarily do anything with otherwise. While it can be wearing, the (imaginary) opponent can provide an interesting and unique experience, as it is innately powerful and relentless, even with a huge pile of weak cards.

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REQUIRED MATERIALS:

-For the opponent:

A large number of Monster cards. (Preferably, Normal Monsters and effectless Fusion, Ritual, Synchro, and Xyz Monsters, and Effect Monsters with simple effects that don't require any decision making processes.) These are the opponent's Deck. Do not separate out Extra Deck Monsters; they go in the opponent's Main Deck. When I say "a large number," we're talking a hundred or more-forty cards is almost certainly too few (although older versions I experimented with needed more cards, I've streamlined things a bit so that fewer cards are more viable) unless you're going to experiment with some of the odder variations.

A standard Duel mat.

-For you:

A playable Yu-Gi-Oh! deck.

A way to track your Life Points. (I recommend keeping a calculator on hand.)


You play as normal; it's your (imaginary) opponent who plays by special rules.


RULE 1: SHIELDS

At the start of the game, put the top five cards of the opponent's Deck face down in the opponent's Magic/Spell/Trap Zones. These are the opponent's Shields. If you've ever played Duel Masters, you'll be familiar with the general idea, but there are some differences here.

When attacking the opponent directly, pick a Shield. That Shield is flipped up, and your attacking Monster's ATK are compared to the Shield Monster's ATK and DEF. If the Shield's ATK OR DEF are higher than the attacking Monster's, the Shield isn't destroyed. If your attacking Monster has lower ATK, it is destroyed. (No damage is inflicted... unless you want to raise the difficulty level. It's still a Damage Step regardless, so you could use cards like Honest normally.)

Shield Monsters aren't treated as Monsters on the Field, and can't be affected by any card effects. (I suppose you could have effects for these Monsters applied, especially if you want to up the difficulty level; just keep in mind that there's no way to counter those effects except get rid of the Shields.)

The opponent has no Life Points. Instead, once you have destroyed all the opponent's Shields, you must simply attack directly one more time to win.

This rule exists primarily to simplify the things you need to keep track of. Only one Life Point total is much easier to track, especially if you're masochistic like me and try to do it in your head. Note that it means your Deck will need to be more focused on battle than your usual play style might be.


RULE 2: OPPONENT SUMMONING PROCESS

The opponent doesn't draw cards or have a hand. (If cards would somehow be added to the opponent's hand, instead they're placed in random order on top of the opponent's Deck.)

Depending on the number of Monsters you control and the number of Monsters the opponent controls (remember, don't count the Shields!), the opponent begins one of two automatic Summoning procedures. The opponent never needs to meet any Summoning requirements of any kind.

If you have any Monsters that are face down, it will place all Monsters in attack mode. It will place all Monsters that have a higher ATK than the current weakest stat among your face up Monsters in attack mode. If it has any Monsters that meet those requirements in defense mode from previous turns, it will switch them to attack mode, too; if it has any Monsters that are weaker than any of your Monsters and have a higher DEF than ATK, it will switch them to defense mode. (Take any stat changes that Monsters may have into account during this process.) Any Monsters it does not choose to Summon in attack mode are summoned in defense mode.

If you choose to give the opponent Flip Effect Monsters or other Monsters with effects that activate when flipped, have it Set them instead (but keep in mind that there shouldn't be any decision-making effects, so the flip effects that actually make sense for the opponent are few and far between).

-SWARM!: If you control more Monsters than the opponent, the opponent Swarms. Start this process by placing the top card of the opponent's Deck face up in the Extra Deck Zone. Check that card's Level or Rank. Then, start taking cards from the top of the opponent's Deck and Special Summoning them, up to the Level/Rank of the card you put in the Extra Deck Zone. If the opponent runs out of Monster Zones and there are still more cards left, put the next card in the Field Zone, and then stop the process. Once you complete this process, put all cards other than the top card of the Extra Deck Zone and the Field Zone that are in those Zones in the opponent's Graveyard.

-SIEGE!: If the opponent controls an equal or greater number of Monsters, the opponent Sieges. If the opponent has an open Monster Zone, the top card of the opponent's Deck is Summoned. Count that card's Level/Rank, and pick up cards from the top of the opponent's Deck equal to that number (if it isn't, put the top card of the opponent's Deck in the Field Zone in the same way you would if Swarming). Attach any cards with the same Attribute as the Summoned Monster to that Monster; these Monsters have their ATK/DEF added to that Monster's. (Don't treat them as Equipment cards, even though that's essentially what they are; just imagine that they're part of the Monster.) This effect can't be negated because it doesn't come from a card, and so regardless of effects such as Imperial Order, Jinzo, or Skill Drain, this stat boost remains. If you want to reduce difficulty somewhat, you can choose to ignore this effect, or to ignore the Swarm procedure (which actually makes games drag out much longer). If you want to raise the difficulty and you're having the opponent use Effect Monsters, you can have the Siege-attached Monsters' effects be added to the Siege Summoned Monsters.

-PURE INSANITY!: For greater difficulty, instead of using the above rules, have the opponent use the Siege Summon procedure, and *then* additionally use the Swarm Summon procedure. (For a slightly lower level of difficulty, have the opponent Swarm, then Siege. Why is it lower difficulty this way? The Siege Summons will be successful less often.) For the highest and most ridiculous level of difficulty possible, use the Swarm Summon procedure, but treat each Monster the opponent Summons as if it has been Siege Summoned.

-STORM!: As an addendum, if you're wondering why you're sticking Monsters in the Extra Deck and Field Zones, it's because of this rule. The ATK/DEF of Monsters whose Attributes match the Attribute of the Monster in the Field Zone are increased by the ATK/DEF of that Monster. To reduce the difficulty, you can ignore this rule (even if the Monsters you give the opponent are weak, they can be quite strong with this effect going), or choose to have Storm only be active if the Attribute of the Monster in the Extra Deck Zone matches the Attribute of the Field Zone Monster.

Note that any cards you have that would interact with the opponent's Extra Deck/Field Zone cards don't interact with these cards, as they aren't following the normal rules for those Zones.

-A note on Xyz Monsters: Obviously, they won't naturally have a way to get their Xyz Materials if you're using these methods. A few possible rules for giving Xyz Monsters their Materials for the opponent:

+If you don't mind the Swarm Summoned Xyz Monsters being at full power, just have all the opponent's Xyz Monsters randomly attach cards from the Graveyard or the top of the Deck equal to their default number of Materials to them.

+If you like the idea of the Siege Summoned Monsters having their full potential effects or more, you can either use the above method only for Siege Summoned Monsters, or have any cards that fail to attach for the Siege stat boost be attached as Xyz Material instead/additionally.


RULE 3: OPPONENT'S BATTLE PHASE

Once the opponent has gone through the turn's Summoning process, the opponent starts attacking. The weakest Monster that can attack attacks a random face down Monster you control (assuming one exists) or the weakest face up Monster you control (randomly choosing between equally weak Monsters). If the opponent controls multiple Monsters with the same ATK, one is randomly selected to attack. If there are no face up Monsters that have an equal or lower ATK or a lower DEF among your Monsters to a Monster that would attack by this procedure, that Monster doesn't attack. If your Field is empty, the opponent attacks with all Monsters, starting with the weakest and working up to the strongest.

Note that this would probably be a robust procedure for programming an AI opponent in a computer game, although not necessarily a smart procedure.


RULE 4: VICTORY

Obviously, if you manage to eliminate all the opponent's Shields and then attack directly again, you win. However, a few other notes are important:

-For a lower difficulty level, have the opponent lose when it decks out, or have it simply sit and do nothing when it would Summon. If the opponent's Deck is particularly thin, I wouldn't necessarily suggest this method.

-For a higher difficulty level, whenever the opponent runs out of cards, pause in the middle of whatever procedure you're performing to shuffle the opponent's Graveyard and replace the Deck with it. This can potentially turn the game into a survival game, as getting through all the opponent's Monsters is difficult when Swarming happens every turn. It also might be a way to allow a thinner opponent Deck to last longer; perhaps you could set some kind of limit, or have the opponent lose a Shield whenever it recycled, and if it has no Shields, it can't recycle.

-For the highest difficulty level, YOU lose when the opponent decks out. I came up with this when the first ever game of the format, in much cruder form, stalled out and the opponent was effectively stalling almost indefinitely despite having lost all its Shields thanks to massive Swarm Summons every turn; if the opponent is weak for whatever reason, this can spice things up a bit.


ADDITIONAL NOTES

-Since I don't mention it elsewhere: You take the first turn.

-Many cards are useless for your Deck in this format. Don't bother with cards like Trap Hole (which only works on Normal Summoned Monsters, although there are fringe cases where it would do something, but I wouldn't recommend it) or Mystical Space Typhoon (your opponent has no Magic/Spell/Trap cards, remember?). Focus on ways to eliminate as many Monsters as possible and then swing in directly with as many Monsters as possible. Also note that certain cards, such as Spirit Reaper and Gravity Bind, are potentially very unfair because the opponent generally has no way to get around them. If you do use cards with long-term defensive effects, it'd be fairer and more fun to stick with cards with once-or-twice per turn effects, such as Fortress Warrior or Scrap-Iron Scarecrow.

-Note that the format has an easy way to increase or decrease the difficulty level of the opponent just by changing up the composition of the opponent's Monsters. More matching Attributes lead to bigger Siege Monsters and Storm effects, and higher Levels/Ranks lead to bigger Swarms and Siege Monsters. If you're having the opponent lose/cease Summoning when it decks out, a thicker Deck will also increase difficulty, although it will decrease difficulty if you're a bit crazy and want the opponent to auto-win when it decks out.

-If you want the opponent to use Effect Monsters and Magic/Spell/Trap cards, keep in mind that they must be simple ones, and you should use the following simple rules and procedures... but note that they add an additional layer of complexity (especially Magic/Spell/Trap Cards).

-Effect Monsters should have effects that don't require decision making, such as paying costs or selecting targets. You can choose to ignore costs for some cards, but others just wouldn't work without costs (e.g., if Cannon Soldier had its cost eliminated, it'd just kill you instantly whenever it was Summoned). Extremely simple decisions, such as "should I do this all-upside thing or not?" can be ignored, e.g. using Grenosaurus's effect, despite having a cost, is a no-brainer-if you can pay the cost, you're going to, and so the opponent always will. If you must have the opponent use targeting effects, have it select the strongest Monster (in terms of its current battle stat) on your Field (if a negative effect) or its own (if a positive effect), or perhaps experiment to see what works best for you.

-Magic/Spell/Trap cards are a slightly more complex issue. I'd suggest that, if you use them, you should keep them simple (Fissure, Dark Hole, etc.) and don't choose any cards for the opponent that have specific timing requirements, as few of those cards make sense at other times. If you're having the opponent use them, during Summoning procedures, if a M/S/T card is the first card flipped up, activate it and then treat the next card as the first card for the procedure. (This means that it will get tons of free activations if you give it lots of M/S/T cards.) During the procedure, whenever an M/S/T card would be "Summoned" or placed in the Field Zone by that procedure, instead activate it, and continue the procedure normally (it does count towards the number of Summons). You probably shouldn't use Continuous M/S/T cards at all, as they'd probably be awkward and confusing without proper Zones to put them in. If a M/S/T card is revealed as a Shield, have the opponent activate it immediately, and it goes to the Graveyard. If you have the opponent use Trap Monsters, treat them as Monsters for the process (ones with timing requirements for the effects that let them be Summoned aren't good choices).

-To make it more fun, while the main purpose of the format is obviously to play a game by yourself, you can form a team of players all up against the opponent. You can ramp up the opponent as necessary; the only way to determine how strong it needs to be is experiment. However, I'm pretty sure it can scale up to a pretty high number of players easily.

-If you're having trouble figuring out how to do something, feel free to ask about it. I think I've covered everything, but I'm hardly perfect.

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Well, there you go. A little late for Make Single People Feel Miserable Day, I guess...

(Once again, if you want to try this out, feel free to ask questions.)

-Signing off.