Yu-Gi-Oh: The Sacred Cards is a GBA video game made by Konami based on the Battle City arc of the Yu-Gi-Oh manga and anime. The plot itself is more or less a Self-Insert Fic of the Battle City arc, with the player character replacing Yugi as the main protagonist. (Yugi himself does appear in the game, albeit with a much smaller role.) The game uses unique rules only vaguely similar to the Yu-Gi-Oh TCG; the most major difference is the addition of Elemental Rock-Paper-Scissors, in which a monster whose type is strong against another's can kill it regardless of Atk/Def points. (For example, a Dark monster of 300 ATK can kill a Light monster of 3,000 ATK, but does no damage to the opponent's Life Points.)The game itself is pretty fun, although it has the nasty tendency to introduce difficulty spikes at points in the game. The game also has a 'deck capacity' limit in order to keep players from adding a bunch of game breaker monsters to their deck and breezing through the entire game, so grinding will be required at certain points through out the game. Overall, it's a pretty fun experience if you can forgive the above.The game got a direct sequel in Yu-Gi-Oh!: Reshef of Destruction, which is much, much more difficult.
This game provides examples of
Ascended Extra: Bandit Keith. While in the anime he was fought and ran off before Battle City even started (and in the original manga, he was killed by Pegasus), here he's a recurring late game boss, and has actualreasons to work for Marik.
Adaptation Induced Plot Hole: Okay, so, in the manga/anime, Yugi gets Osiris/Slifer by defeating Pantomimer (Strings in the localization). In this game, the player is the one who duels Pantomimer. You don't get Osiris from your victory over Pantomimer, and Pantomimer is never heard from again. During the finals, Yugi's deck has Osiris. How on Earth did he get that card if he never dueled Pantomimer?
He happened to find Pantomimer's comatose body and checked his deck? It does seem OOC for him. Meanwhile, if the player won, they probably didn't get a good look at Osiris and didn't realize that they might want it.
Awesome, but Impractical: The Egyptian God Cards of course. Once they're on the field, you (Or Pantomimer/Strings, Ishizu, Rishid/Odion, Dark Yugi/Yami Yugi, or Marik) have essentially won. But once you're doing well enough to have enough tributes to summon them, you could probably have won without them.
Same goes for Ritual Monsters in this game. You need a certain monster (For example: Mask of Darkness for Mask of Shine And Dark which comes in your starting deck), two other monsters, and the appropriate spell card. That's four cards, two of which have to be played together. Although, if you get them out, the balance quickly shifts into your favor since Elemental Rock-Paper-Scissors can't kill a Ritual monster as they are all Divine-class and most of them have a LOT of attack points.
Boring Yet Practical: The weaker Tribute monsters for much of the game, since they may only have 1800 ATK for one Tribute, but your normal monsters at best have 900.
Doron. You start off with one, and it has a low deck capacity cost, and an ATK of 900. More importantly, it has the ability to duplicate it's self when played, which is really useful for tribute summons. Later, you can win a Revival Jem, which has the exact same attributes as Doron, but has 600 more ATK at the cost of a bit higher deck capacity limit.
But Thou Must: In the ending, you have to turn all three Egyptian God Cards over to Ishizu, never getting the chance to use Ra even once.
Death by Adaptation: With you in the finals in place of Ishizu, you're the one who duels Rishid/Odion, and in the semi-finals Yami Yugi. This leaves Joey and Kaiba to duel Dark Marik, and it goes as well as you'd expect.
Demoted to Extra: Yugi. A painful example since the story still revolves around Marik seeking the God Cards and destroying Dark Yugi, yet you're the one who faces all the Ghouls/Rare Hunters and Yugi is basically not in the game until the finals begin.
Jonouchi/Joey, too, since you defeat all of the players that he dueled in the manga/anime.
Doppelgänger Attack: Strings is a shining example. Numerous monsters summon other monsters into play, two — Doron and Revival Jam — directly summoning another copy of themselves, and Strings specializes in such monsters.
Full-Name Basis: Interestingly, whenever Marik Ishtar is referred to or addressed by name in this game (which is often) it's Always as "Marik Ishtar".
NPC Roadblock: Many areas will be blocked off by KC guards or Ghouls until you have passed a certain point in the story. Most notable is the Museum, the outside of which is accessible at the start of the game, but which is blocked off until shortly before the finals.
Level Grinding: The easiest way to get your level up quickly in the final levels is to stack your deck with Shadow and Fiend monsters when it comes time to duel Ishizu, curbstomp her Light and Dream monsters for 30 deck points and a rare card, then lose to Kaiba on purpose. When you return to the museum you have to start over with Ishizu again, giving you 30 deck points each time. This method was notably Nerfed to the point it's unusable in Reshef of Destruction.
Self-Insert Fic: The easiest way to sum up the plot is that basically the player character combines the roles Yugi and Jonouchi played in the manga/anime during the Battle City Tournament arc, with Yugi and Jonouchi themselves basically reduced to supporting characters.