RNG Manipulation
RNG is fairy robust in Robotrek. To my knowledge, there are only really a few ways to manipulate the RNG chain, with most being unavailable to the player. NPC and enemies will roll the chain forward to determine their movement. Secondly, the frame time is used in the RNG chain as well. In order to manipulate RNG, you have to wait until an enemy moves and/or wait a frame. This allows for much easier manipulation of capsules in battle, capsules appearing out of battle, capsule contents, enemy positions, NPC positions, and critical hits. Unfortunately, this also means changing actions earlier has an effect on future actions, and an added bonus of "desyncing" any work already done past that point. For instance, I take 5 HP at the beginning of the game and only end up taking 1 damage. Changing this to 2 HP would affect any other RNG derived decision that came afterwards.
Blocking
Blocking is fixed at a 25% chance for the robot and enemies, but is based on the 2 additional factors. First, the global frame counter (including lag frames). Blocking is based on a 32-frame cycle, where the first 24 frames will fail to block, but the next 8 frames are eligible for successful blocking. Second, blocking is dependent on the player having a piece of equipment that grants the ability to block. Any equipment that provides a defense bonus will also provide the ability to block.
ATB/Fuel Meter
Briefly, as the compendium does a much better job of explaining it (see Special Thanks), the ATB replenishes based on the robot's charge stat but has some unique quirks. The game allows the player to aid refueling the robot between turns. To accomplish this, every time the player pushes the B button, fill time is reduced by 8 frames, but is placed on an 8 frame cooldown. This bonus is disabled once the charge stat is equal to or greater than 50. This TAS makes extensive use of this feature, in combination with a variety of attacks, to stop enemies from getting multiple turns, and in some case a single turn.
Item manipulation
After battle, loot can drop in the form of capsules. Provided one or no enemies are around to affect the RNG, a capsule will drop with a 25% chance. The underlying mechanism is more complex, but in practice, this means within every 4 frame window, a capsule drop will occur. This window appears to be tied to the frame count and the value of 0x052A ending in 0. Each enemy formation has it's own loot table, and loot can be dropped from 3 categories: Common, Rare (1/16), and Super-rare (1/256). Capsule contents are determined upon opening. For practical purposes, the game reads the byte at 0x052A to determine the rarity. If the byte ends with 0 (e.g. A0), a rare drop will occur. If the byte is equal to 00, a super-rare drop will occur. All other values produce common loot. Fortunately, this address is a part of the game's RNG chain. With this knowledge, and knowledge of the enemy and NPC movement rolling the RNG chain, it's easy to get any item tier drop with little waiting. The only caveat being the super-rare drop may involve a longer wait if fewer enemies are around. Finally, the capsule needs to be opened on the value prior to the desired outcome (e.g. values of: 27, AD, 90; the capsule needs to be opened when the value is AD), since the outcome needs to be the value (e.g. 90 for a rare drop) when the capsule is actually open.
Other strategies
Run past enemies
The game initiates combat when you touch an enemy, and gives initiative to the player or enemy. Unfortunately, there are a few places where the player doesn't have a 1-tile offset to avoid a battle. Normally, the player's choices are to battle or run away. With this technique, the player must come to a complete stop and allow the enemy to initiate a battle. However, opening the player's menu can interrupt this check and the enemy's momentum will propel it passed the player. The game's RNG will determine if this action is successful, but it isn't difficult to setup or succeed.
Enemy tactics change
As mentioned before, there are very few ways to manipulate the RNG directly, and even fewer in the heat of battle. On the final boss, I use guarding to forcefully change the boss's attack pattern. This technique is not always successful, but changes the boss's next attack to the ram attack. The ram attack can usually be blocked provided the player has blocking enabled equipment. I did find instances of bosses waiting to use the ram attack on the first non-blocking frame, meaning taking damage was unavoidable. There are no instances of this happening in the TAS, but is stated here for others interested in this game. The mechanism behind this this technique and the ram attack issue needs to be further explored to understand how they actually work.
Other Comments
NPCs have set path routing, and usually walk very slow. If the player doesn't approach from a position not blocking their set path, they will walk slowly around you. It always faster to avoid this, except in cases where you have to approach from the front to progress the plot.
NPCs typically roam around randomly when onscreen. In the event that I need to talk to them or need them to go somewhere, I manipulate them to be as close to the player or their destination as possible. In dungeons, wherever possible, I manipulate enemies to move away from the player, or move aside to allow unimpeded passage.
Route Summary
I settled on minimizing encounters to save time. Still, there were 6 non-forced encounters taken to go flesh out the route: (1) Gel (2) Spider (3-6) Shells. For battle information, see the Battle Guide tab. The need for any gold is eliminated in this version of the TAS, as well as crafting and combining to upgrade weapons.
Rococo - Cave
I need to reach level 2 at a specific point to save time. I start by making the robot and going all in on power. I take 5 HP as for safety since I didn't know how well farming capsules would be while also defeating enemies. I grab the Scrap 5 from the tool shop, but I don't take the hidden repair next to it. At father's house I grab a repair (one is required to beat the game) and a clean before heading out again. I considered manipulating these drops, but these two items are close enough to each other that it's faster to collect them here.
Outside of father's house I take the first battle and manipulate a 1.0 EXP bonus capsule. In the cave, I grab the drill, and manipulate another 1.0 EXP capsule. After leveling, I use the portable R&D to clean the drill and remove the blockage. Spiders are super dangerous at low level and even more-so with low defense stats. I manipulate a single spider battle and a capsule drop as well. There are three enemies around when the capsule drops, but the hidden gel doesn't roll the RNG chain forward. I manage to get a super rare drop (Punch 2) in a reasonable amount of time from the two spiders pushing the chain forward. The trade-off is the more I manipulate on the front end, the more time I lose on the back-end.
The next two battles are about boosting EXP to hit level 3 before fighting Meta Crab. Using the Punch 2 and Scrap 4 I grabbed along the way, I make Punch 3 and OHKO Meta Crab.
Family Shrine - Clocktower
I grab the Shield 2 and now have a piece of equipment that allows us to block. I force equipment level up in the next 8 battles to max our weapon as soon as possible. I begin by defeating 2 monks. I wasn't able to maniuplate a 3 monk battle with an equipment leveling capsule without wasting a lot of time, so I settled for 2 Monks. I sacrifice a one turn OHKO on Mamurana to level up our equipment.
South Isle - Biolab
In the older version of this TAS, I leveled up the weapon by crafting and combining Punch 1s to our Punch 3. This process takes 3 minutes, so manipulating level up capsules in battles is much faster. I get the final equipment level on the Big Eye boss fight, again sacrificing a one-turn OHKO for equipment leveling. I also grab a Scrap 9 along the way. I could have manipulated Scrap 9 as a rare drop, but the extra battles more cost time versus getting free ones along the way.
Sewers - Mayor's House
The shell formations fought in the sewer are the only ones that have up to 3 shells. I need 8 shells to reach level 20, so I manipulate 3 per battle with the intent to defeat at least 2 in each battle. I would have opted for a 3-3-2 configuration, but defeating 3 in each battle proved harder and longer than I thought. Anyways, I reach level 20, and dispose of a few hackers and Papamecha. At this point, I prioritize single enemy encounters to save time. I make vanish and proceed.
Snow Harbor - Snow Base
Primarily plot and backtracking. I OHKO Bugbug by 1 HP then collect a second Scrap 9 afterwards on the way to the next boss. Blacktank is the first boss that cannot be OHKO'd. I manipulate a ram attack and two critical hits to finish the battle quickly.
Old Rococo
The cave section after the time slip is mostly uneventful. However, I discovered that in this dungeon, and a few other places I haven't mentioned this for before, the RNG is static. The only way to move it forward is through battle. This presented a few challenges for the boss because her attack patterns were not what I wanted. Still with decent critical luck, I managed to defeat her 2 seconds slower than a test battle where she primarily used the head smash ram attack. This will be one location to further optimize in a future update of this TAS.
Outer space - Fortress
I grab Shield 4 here for the final boss. I take a single enemy battle and end the game with 3 boss fights. I manipulated a pretty good Bugbug 2 fight, although I would have preferred more "hockey puck" attacks since they can be blocked.
Gateau 1 - This was an extremely difficult battle. The soldiers have 2 attacks, a gun shot that cannot be blocked, and a gun shot that cannot be blocked but can disable your run commands. Meanwhile, Gateau has a gun shot that cannot be blocked and a screen flash attach that can be blocked. Similar to the unavoidable damage issue I mentioned in the enemy tactics change section above, Gateau can perform the screen flash in this manner as well. I managed to manipulate some pretty insane critical luck while also not being disabled once. This dropped the fight to 47 seconds instead of a really good 2 minute fight I practiced prior.
Gateau 2 - Another difficult battle. Similar to the old cave section, the RNG chain is static again after the Gateau 1 battle. I would need to traverse several rooms backwards to get a better RNG 'seed' to start this battle. Initially, I had a great battle that began with 3 critical attacks, but the next 15 attacks would not critical hit, making this a long slow fight, so I started over. Because the 'seed' I went with wasn't great, I wasn't able to get a consistent amount of ram attacks to save time. I did allow one beach soldier attack because the remainder of the battle went quickly. I use Shield 4 here because of a programming bug that essentially reduced damage of the wrong value. In practice, I take 1-2 damage from elemental attacks and attacks that make the robot flash red (e.g. disable attacks from G1 soldiers). Due to not having more equipment like the Shield pack, this is the best way to avoid taking a ton of damage with lower evasion. This is ideal because 3 of Gateau's attacks in this form are elemental attacks. The other attacks, except for the beach soldiers attack, I manipulate away by strategic guarding.
Software:
- ROM: Robotrek (USA).sfc
- SHA-1: e315830e71cc6da91234813f70835d26802c0ea1
- MD5: e85702f5d32e03a7cbae1154ee5083ce
Suggested Screenshots
- Frame: 515879
- Frame: 340499
