Resurrecting this thread as I'm currently working on a TAS of Boktai 2, and progress has been much faster than I anticipated thanks to the help of the very talented minds over at the Taiyoh Network Discord server.
Boktai 2 is separated into several dungeons that must be done in sequential order: Cathedral, Remains, Dark City, Aqueduct, Spiral Tower, Undead Zone. No current means exist to sequence-break these or skip any story events, and even if you could, most of your loadout obtained through story events is required for Undead Zone.
Previous attempts from others at this game didn't appear to get very far, I'm currently on the interim leg between Dark City and Aqueduct, so just over halfway through the final movie file. The biggest impediment to progress has been the EXP routing, and RNG manipulation; I had to redo Remains twice due to simple arithmetic errors in my EXP routing, even whilst working on a spreadsheet using formulas.
As far as working with RNG goes in this game, the golden memory value is 46B8 found in IWRAM. which will henceforth be referred to as RNG2. RNG2 is what controls all of the random events that we care about, such as weapons dropped by enemies, forge results and other area-specific random calls. It is a value that defaults to 833 after booting the ROM, then progresses until 1023, after which it overflows to 0 and cycles again. Thus, RNG2 is always an integer between 0-1023, and is progressed by different events. Some of these are automatic, and some of these can be caused by the player. Of note is the drop table, which was published some time ago by the previous RTA WR holder, Coa, and shows which RNG2 values are required when a random drop check is called to get either a Common item or a Rare item. In virtually all cases, we are interested in Rare items, which can drop on 12 of the possible 1024 RNG2 values, approximately a 1.2% chance. 7 of these are obtained over the course of the run so far, with a planned collection of two copies of a specific tarot card, "The Tower", which is on a separate drop table at a rate of 40/1024, or 3.91%.
The most critical element of the route by far has been forging a Katana at the earliest possible opportunity. Some posts were previously made about getting access to better weapons, and which weapons would be best to take into the boss of Dark City, Red Durathror. Something that these posts omitted is that weapons in this game are level-locked; it would do no good to magically get the best weapon in the game to drop, because you're not a high-enough level to equip it at any point in an RTA run, let alone a TAS. By the point that forging becomes relevant, you are generally Lvl 12. The best weapon you can reasonably take into the next dungeon (Dark City) is the Lvl 13 sword, Long Sword. Hammers and Spears are also usable in this game, but Swords are overwhelmingly the best weapon choice due to their attack speed.
However, the TAS route hinges on crafting a Katana, which is a Lvl 17 weapon, then taking the most efficient EXP grind possible in order to be able to equip it for the boss fights in Dark City. This sounds like a sub-optimal solution, but the timeloss of taking your next-best options into Durathror is much worse, to the tune of a few minutes. Getting the Katana craft to work at all was a near-impossibility, we knew it should have been theoretically possible, but it had never actually been proven in RTA play.
First of all, I needed eligible craft materials. Forging in this game follows different rules depending on which types of weapons you use as materials; same-type weapons will always result in a weapon of that type, whilst different-type weapons will result in the remaining type. In order words, Sword+Sword will always create a Sword, whilst Hammer+Spear will also always create a Sword. However, where these situations differ is the level modifier applied to the resulting weapon. When using same-type weapons, the game will tell you explicitly which weapon you will get as a result of the forge, because a high level modifier is applied to the resulting weapon; the result of a forge is (Weapon A Level + Weapon B Level) / 2 + r, where r = 6 when materials are of the same type. You will always get the highest-level weapon that does not exceed the final level value. As a practical example:
Short Sword (Lvl5) + Broadsword (Lvl9) = Long Sword (Lvl13)
(5 + 9) / 2 + 6 = 13
This is simple enough for same-type weapons, but when different-type weapons are used, r will become a random number between -6 to +6. In the above scenario, the +6 bonus is necessary to create the Long Sword, and any lower value results in a Broadsword, as it is the next-highest weapon after the Lvl13 Long Sword. This is a problem for the TAS route, because we don't have access to high-level swords as crafting materials! The only high-level weapons that can be manipulated during Remains are Maces, the Lvl 9 Hammer. We must do two crafts to get the Katana, and they're both different-type crafts, which turns our automatic +6 weapon level bonus into a random -6 to +6 bonus. Only +6 works, so both crafts are now a 1/13 chance to result in the correct weapon. Thus, the craft route becomes:
Short Sword (Lvl5) + Mace (Lvl9) = Lance (Lvl13 Spear)
Lance (Lvl13) + Mace (Lvl9) = Katana (Lvl17 Sword)
But we're not done yet, the Lvl17 Sword is the Zweihander, not the Katana. At least, that's the weapon you'll get 99 times out of 100. The Katana is an "R-rank" weapon, essentially a Rare craft. An additional check is performed when initiating the craft to see if the weapon will be eligible to progress to "R-rank", which for all intents and purposes means hitting a short frame window; in the TAS I have a 1% chance of getting an R-rank craft, which is defined as starting the craft in a 4-frame window, on a framerule of 400. If the craft is successfully started at the correct time, RNG2 must also be at the correct value when the forge finishes in order for the resulting weapon to be the Katana instead of the Zweihander... And I have next to no control over how RNG2 advances during the forges. Additionally, I'm trying to apply an extra variable during the Katana forge by giving the weapon its "SP effect", which is granting extra attack power based on your Agility stat. Thankfully, this variable is skipped in practical terms by simply doing enough strikes in the forge to grant a 100% chance for SP effect acquisition, which also allowed me to finish on the correct RNG2 value to get the Katana SP.
After gaining this weapon, it's basically "go-mode", just get to the end of the game as fast as possible. No weapons later in the game are worth taking the time to collect and use, as the Katana remains a competitive damage option up to and including the final boss, and due to its SP effect it punches even further above its weight (Essentially gives you +6 Strength) and never suffers durability loss that forged weapons normally suffer over time, which causes their damage to degrade over time and causes undesirable lag whenever this degradation occurs.
My current WIP file should be available for download through my uploaded files, and should sync on the newest Bizhawk release, 2.9.2. I'm using the unmodified JP 1.0 ROM, so don't attempt to play the movie on a patched ROM or it will not sync.
