• Emulator used: various, but final run is synced on BizHawk 2.4
• Aims for fastest time
• Takes damage to save time
• Uses game restart sequences
• Heavy luck manipulation
• Heavy glitch abuse
• Heavy abuse of the game's poor event script
• Heavy abuse of the English language

Digimon Ruby (also known as Digimon Rury, as it is written on its box-art) is a bootleg role-playing game developed by Taiwanese bootleg game developer Vast Fame (known for games including Zook Hero Z, Rockman DX3, Devil Island, and Zook Man ZX4).

Throughout its existence from circa 1998 to 2003, Vast Fame developed various Game Boy games and a few Game Boy Advance games. Most of their games are either platform games (generally heavily inspired by Mega Man games) or role-playing games (generally inspired by Pokémon, often taking after Digimon). This game is a clear example of the latter.

Vast Fame games are generally known for being relatively high quality for unlicensed developers, with original stories, reasonably solid gameplay, and surprisingly decent music (helped by the fact that they took the sound engine from Mega Man V for many of their games). They are also known for their rather spotty grasp of the English language, for any games they made English versions of.

Digimon Ruby is one of Vast Fame's last games, released circa 2003. Unlike most of their other Game Boy Advance games, it uses Direct Sound for its title screen music and for percussion in the game's soundtrack, but retains the use of chiptune audio for everything else.

As noted before, Digimon Ruby is a role-playing game. The plot centers around Davis/Daisuke Motomiya (known as DaFu in this game), of Digimon Adventure 02 fame. During a school picnic, DaFu is transported by a mysterious portal to the Digimon World ("figures world"), and he has to find a way to return back to the human world while uncovering and stopping evil influences along the way.

The foundations of this run started up back in the middle of 2014. This was when I first discovered the game, and started data mining just to be able to get the resources needed to devise a route.

One of the first challenges that comes with routing for this game is how ridiculously grindy it is at its core. If you want to fight the final boss on even terms, you would need to reach level 74. This takes around 420k experience points. If you were to grind in the final area of the game (filled likewise with lv73-74 enemies, you get ~800 exp apiece, so you'd need to beat more than 500 of those. With a more realistic progression spread (starting all the way from enemies that give between 2 and 6 experience in the first area), you're easily looking at several thousand monsters of grinding just to be able to have a chance in th end-game.

At this time, I gathered knowledge about several aspects of the game, including the full lists of 171 Digimon in the game with their stats, the experience curve, 166 moves, 625 encounter data instances, and 16 items. However, I eventually got stuck routing out how to effectively get past the second boss (let alone everything else), and let it slide for a few years.

Fast forward on five years later, when I decided with a better grasp of scripting and using information, I would be able to at least mathematically devise a way to get past all the bosses in the game, or find a shortcut, if any. An important part of the new data gathering was getting complete info about all Digimon availability and learnsets, to get a proper idea about what options were available, and if there were any particularly good ones.

Eventually, I found an important breakthrough: a pair of absorbing moves, which would always deal exactly 10% damage. When considering the odds we generally are up against in the run, 10% is a lot. There were a few different ways to access them, but following multiple rounds of testing (and uncovering a few hiccups along the way, such as a bug that prevented some Digimon from learning a certain move when that was exactly the move I needed), I found the most optimal solution to be to have the 'mon Bada Beast, who learns the absorbing move Blood-Suck Needle at level 15. And could beat the final boss with it in a testing environment. This shortened the projected runtime by a lot.

With that, along with mapping out the locations so I would know where to find Upgrade Badges to skip the heaviest part of leveling, it was possible at last to set up a leveling route. This route comes down to: Dark Tower lv1-lv4, Steaming Hot Desert (boss only), Spiral Mountain lv4-lv8, Opacification Forest lv8-lv13, and the final two levels fulfilled with Upgrade Badges. The rest of the game could be done without need of further grinding.

Once I had the route figured out, it was really just a matter of executing it. Tricks like skipping bosses, Dark Crystals, and other plot-related events also added up nice time-savers, but none that affected the main scope of the route all that much. Most of the main storyline is still played out as normal, and the final bosses still need to be fought like normal.

In classic style of Pokémon and similar RPGs, you can have a party of up to 6 Digimon which can all level up as they gain experience throughout battle. Digimon also learn new moves as they level up. Experience requirements increase per level but are otherwise identical for every Digimon.

The player can obtain up to 7 different Digimon; one starter, and six that are found in various chests throughout the first island. If the player finds a chest while already having the max of 6 Digimon, it will open but the player will not get the Digimon. However, the player has the option to "Transfer"/discard Digimon, to free up a slot if desired.

Stats

Moves

Items

Digivolution

Move learning

Encounters and bosses

This game's RNG is an absolute pain, and provides just the bare essentials to have something to work with at all. It only ever updates when it is called (and not on a frame or input basis), which drastically limits the room for manipulation you have.

Fortunately, there is a single way to advance the RNG without much in the way of side effects - this is by switching Digimon in battle, which is a free action (most of the time), can advance RNG once or twice depending on where the switched Digimon are in the party, and costs around 20 frames per use. It works, but it does result in some very visible switching situations now and then, sometimes upwards to, say, 5 seconds of switching.

DaFu's hitbox when moving in the overworld is effectively a small rectangle, which extends further to his front than his sides. Because of this, it is possible to clip deeper into a wall than simply walking into it, by instead approaching it from the side if possible. Normally this is not that interesting, but on rare occasions there's some interesting level geometry that results in things like one-way paths.

Illustrated above is an example of overworld hitbox visualization, as well as geometry forcing an one-way path: it is not possible to go through this tight pass from the left side, but it is possible to go through from the right side.

Encounters in this game basically function on a walking timer: the timer is randomly initialized between 256 and 511, and subtracted by 1 on every frame of walking in a wild environment (outside of town). If it hits 0, an encounter is triggered (with further RNG calls to determine the specific encounter).

The timer thing means there's a slight bit of leeway for manipulation to reduce/minimize encounters, but they cannot be removed entirely. It's also possible with in-battle manipulation to determine the type of the next encounter, which is useful for grinding (making sure to get the most beneficial encounters for experience).

When the player steps into a screen transition, and keeps holding onto that direction, the player will do 1 frame step in the middle of the transition into the new room (before the fade-in). If in this 1 frame the player triggers an encounter, the game will stop loading the new room and trigger the encounter instead.

As a result, after the encounter has ended and when the player returns to the overworld, the player will be in the new room, but event triggers will not be loaded. This primarily affects chests, NPCs, and similar objects; the chests, NPCs and objects from the previous room are still loaded in memory, so the player can interact with them in the new screen, if they are reachable.

The new screen's objects are not loaded, so this can help if for example an object is physically blocking a path to something. The old screen objects still send events when triggered, now to an event table that has been updated for the new screen - so the interaction will now trigger an unintended event.

More often than not, this results in crashing the game. However, sometimes, the object's event will align with a new event in the room, resulting in effects such as opening a different chest, or starting dialogue with an NPC that would be in the room, or interacting with an object that would be in the room. On some occasions, this can be used to skip an event (or a boss battle) or sequence-break to an event earlier than should normally be possible. In these cases, significant amounts of time can be saved with this trick.

The game's script (as in plot progression requirements) is...less than solid. The plot can tell you to destroy a Dark Crystal, when in reality the script will ignore the flag about the destruction of that crystal entirely, and it would speed things up significantly if you avoid doing so.

Therefore, an important aspect of routing is not simply looking at what the game tells you to do, but to find precisely which flags need to be set in order to allow the next event to happen or dialogue to be unlocked. This will result in some comical situations, most notably in various instances where some major plot items are just walked by and completely ignored.

Due to how Digivolution branching works, it is possible to have multiple instances of the same Digimon species. If this is the case, the game gets confused when trying to switch to the unit during battle.

Essentially, if the player tries to switch to the first (in party order) Digimon, it will copy its stats to the second Digimon. Conversely, if the player tries to switch to the second Digimon, it will take the stats from the first Digimon. In both cases, the first Digimon will in effect be brought into the battle, unless it is fainted. As a result of these glitches, it effectively becomes possible in a battle to make a save-state of the Digimon by switching to the first one, and then loading it by switching to the second one.

This mainly is convenient because it makes HP and MP management very simple, as both can easily be refilled at any time just by switching to the second instance Digimon. MP-restoring items become essentially obsolete with this trick.

• 0x5E37CC - Experience level-up table (24 bytes per level, 99 levels)
• 0x5E42A4 - Digimon stat table (24 bytes per digimon, 171 digimon)
• 0x5E555C - Experience curve (99 levels)
• 0x622E48 - Move MP cost table
• 0x6230A4 - Move damage table
• 0x6234D4 - Digimon learnset table (60 bytes per digimon, 171 digimon)
• 0x625F98 - Encounter data table

General game data

Overworld data

Battle data

Digimon data

Obt. means that the Digimon is obtainable by the player (as a starter, from chests, or as a Digivolution of an obtainable Digimon)

Notes about move learnsets:

• Due to a bug, the first move of a stage 1 Digimon is always Air Bulb, even if the learnset says something else.
• Due to another bug, the "Lv8" move of a stage 2 Digimon is never learned.

All encounters with a Party ID above 0 are part of a party of the previous encounter. For example, if [E14] appears as a wild encounter, it will consist of both Digimon of [E14] and [E15] as part of one battle. Only the former's EXP and Gold counts are used, and all Digimon in the party must be beaten to receive the rewards.

Encounters from [E593] to [E625] are boss encounters, and cannot be escaped from.