I've been making a serious attempt at checking out how various categories in this run work. Here are my results:
- Glitched low%: there's a large-skip glitch in older versions of the game that lets you go from GrottoEye directly to Final Climb (proven), and probably the final boss (not proven yet but only because the person who did it can't remember what they did to manage it). However, that glitch has been fixed in more recent versions, so it would have to be done on an old version. The percentage achievable like this is believed to be 9%; it's been done on console, and requires several upgrades that are only used in one place (which is annoying, but seems unavoidable).
- Unglitched low%: uninteresting; none of the upgrades that would seem really interesting to skip are skippable. (In particular, Stick Slide is required to complete BlackCastle, and it has Teleport and Stick as prerequisites, and going from there there's pretty much nothing interesting skippable left.) This is the case on any difficulty, because BlackCastle is the skipping point.
- Any% and 100%: the only interesting categories IMO, but both are interesting. The question remains of what difficulty to use: the viable choices seem to be Easy (for fastest possible run), Masterful (highest difficulty unlocked at the start), Insanity (a secret difficulty; I haven't unlocked it myself, but I've heard that it's unlocked by completing the game on Masterful). As far as I know, the only difference between Masterful and Insanity is that all damage sources one-shot the character on Insanity, leading to an enforced no-damage run, whereas it's possible to survive hits on Masterful (even though they deal 2.5 times as much damage as on normal difficulty). I think it would be most interesting to do the any% on Insanity and the 100% on Masterful; the reason for this is that an any% isn't going to be able to do much damage boosting anyway, because it won't have the HP for it, whereas if any category can afford the HP for damage boosts, it's going to be a 100%. This way, the parts of the game that would otherwise be the same in any% and 100% would look different.
In terms of routeplanning the game, the first thing to note is that the game is structured into a few areas with a natural progression between them. The most vital restrictions are:
- You need Hatch and Dive Bomb to progress to the second part of Farfall, FireCage, DeepDive, or Deep Grotto. This is the most vital thing to realise in route planning, as you need to complete almost all the areas you can access before this in order to progress beyond them. (To get these upgrades you need to complete StoneCastle (red energy section) and NightClimb, which require buying red energy and completing DeepTower respectively.) You don't need to complete ColdKeep before doing this, but as far as I can tell, there's absolutely no reason why you'd want to put it off until later, and you need to do it eventually.
- You need yellow energy, Stick Slide, and all six jump upgrades to make any significant progress in The Curtain. In other words, all the upgrades that matter must be done before progressing to the top-right area of the map.
Also, the order of the major routing details start of the run, as far as I can tell, is obvious, in either any% or 100% (100% would be collecting red hearts along the way, obviously, although it's not clear whether some of the hearts in NightWalk are best collected at the first opportunity or later):
First, the absolutely unavoidable sequence:
NightWalk -> jump upgrade 1 -> Grotto -> GrottoRed (boss) -> double jump ->
Next, something that isn't technically required but is obviously better than skipping upgrades that will definitely be needed later:
DeepTower -> DeepCannon (boss) -> shoot fire -> jump upgrade 2
(For a 100% run, you'd collect the heart in the open in Coldkeep directly below you, and also the heart across the spike trap in DeepTower, right now, if it's technically possible to get both of them. I think it's doable with just three jump-related upgrades, but that needs testing. Obviously best to do it now in a 100% if you can because otherwise you'd be backtracking to an area of deeptower you have no reason to visit later on to get them. An any% would skip them, as they're two relatively slow hearts.)
The big question here is which way to go in ColdKeep, but I have a strong suspicion that NightClimb first is the fastest route, especially in a 100% run. (Of course, it needs testing.)
Advantages for NightClimb first:
- Red Energy is unhelpful in NightClimb or ColdKeep so there's no point in getting it first
- Dive Bomb is only marginally useful in NightClimb (it speeds up getting from the top NightClimb save to the chest and ColdBlob; I believe going that way is faster than going from the bottom save point if you want the chest, and of course you have to go that way anyway if you're doing this before Teleport)
- Considerably less backtracking is involved; the alternative would be to activate the NightClimb save point, then move onto SkyTown and teleport back later, then find some save after ColdBlob to teleport back out
- I'm not convinced that StoneTower can be done without Stick without taking damage in the higher difficulties (one of the flame geysers seems impossible to pass fast enough without waiting on the ceiling for a cycle), maybe I just suck; a 100% on Masterful could just take the damage here, but Insanity couldn't and an any% would need at least one red heart
- More crystals before SkyTown lets you do more shopping on your first trip (this one's dubious, you should be able to afford the red energy boost anyway, and you probably won't be able to afford long shot anyway which is the only other thing it'd be beneficial to buy on your first trip as opposed to a later trip, except the gold orb but no chance of affording that)
Advantages for SkyTown + StoneCastle first:
- Duck is useless in StoneCastle (and pretty much everywhere else for that matter, lol)
- You could teleport out from the top NightClimb save rather than having to jump out, which is faster if you've got nowhere else to go (which may be the case in any% if you're reaching ColdBlob some other way, and probably isn't the case in 100%)
- Being able to dive bomb speeds up falling from high places like the top NightClimb save point slightly
Either way, if you can defeat a boss before Hatch + Dive Bomb, you'd want to, because there's no reason not to. So all routes converge once you have Hatch, Dive Bomb, Energy Boost 1 ("red energy"), Shoot Fire, Duck, Stick, and at least 4 of the 5 possible jump-related upgrades (you don't technically need this many upgrades for FarBall and thus StrangeCastle, but you do to go anywhere else of interest; and the StoneCastle jump upgrade is on the way, so you'd definitely get that one, when to get the SkyTown double jump upgrade is less clear).
One other thing to consider is where to get Teleport. It's available either from SkyTown or StoneCastle (or other places but those two are the only two sensible ones); it's less distance out of the way in StoneCastle, but you need to get it in SkyTown if you're getting Double-Jump Upgrade 1 immediately rather than waiting until after StoneCastle.
Once you've passed the point of route converging, there are only really four more upgrades whose order (relative to each other, and to areas you go through) is interesting: Double-Jump Upgrade 2 (in FireCage), Stick Slide (in Skysand), Shoot Ice (in DeepDive), Energy Boost 2 ("yellow energy", also in FireCage). The important factor to note here is that you're going to have to make two trips through DeepDive (technically you could do it in one, but I suspect backtracking after DeepSerpent is going to be slower than just teleporting out and coming back in from Grotto, although of course this needs testing). The obvious thing to do in a 100%, at least, is to get Shoot Ice, Air Upgrade 1, and maybe Air Upgrade 2 and the surrounding other items in the first trip, then go onto Blancland and get all the items en route to there. Then on the second trip, you collect the hearts at the top of DeepDive (you can't get them all on the first trip, you run out of air), beat DeepSerpent, and collect everything on the way up to LongBeach. (You'd want to have started the ghostly flowers quest by this point, to allow you to simply teleport out after Deep Grotto rather than having to climb up to LongBeach again.) An any% will still need Air Upgrade 1 as otherwise I don't think it can reach BlancLand, but it's less clear whether it should try to do things all in one go.
Complicating the issues: you need Shoot Ice before Stick Slide; you want Shoot Ice before any of FireCage (it saves a noticeable amount of time on the thwomp-like things, unless you're planning to just let them hit you, which you can't do in an any% as you won't survive and you can't do in a 100% as there's a heart door); you want all the jump upgrades before doing SkySand (it's noticeably faster because you can go straight from one red cluster to the next rather than having to take detours); in a 100%, you also want yellow energy before SkySand (there's a heart that can only be reached with it, so if you don't have yellow energy by then you're going to have to redo it), and in a 100% you want Stick Slide for BlancBlock (strictly speaking not for the boss itself, but it's needed to collect a heart afterwards). Note that BlancBlock (along with about half of BlancLand) is skippable in any%, and in a 100% it's fastest to reach it by using the skip and then entering the boss room from behind (bosses count towards percentage, so you'd have to fight it). And doing the BlancLand skip just before the boss+gold orb is fastest purely due to cursor movement time, although that's probably not a large factor. Also, there's a heart in BlancLand (the freeze-the-triangles heart) which is virtually impossible in non-TAS conditions without Long Shot; I'm not sure if it's doable without it in a TAS, though, or how much time (if any) would be lost.
Now, this mess can be sorted out easily by using the save point halfway through FireCage; a 100% has to use that anyway because it's aiming for Bonus, but an any% would probably want to avoid it, unless it's really necessary. Strangely, though, that only seems useful if we're doing SkySand the moment we get Stick Slide, and we aren't because that would mean not having it through the first half of Firecage, which is worse than the cost of a couple of teleports.
So a tentative route through this second section of the game looks like this:
Grotto->GrottoEye->DeepDive->Shoot Ice->Air Upgrade 1->BlancLand->BlancBlock skip->(in an any% get BlancLand orb now, in a 100% don't get BlancLand orb yet, just teleport out)->NightClimb->SkySand->activate SkySand teleporter->heart on the watchtower in SkyTown (this isn't the only way to get it, but it fits nicely into the route just here)->perhaps buy Long Shot, not sure if we need it, how much it saves or if we can get it earlier->Stick Slide->teleport to Grotto->FireCage->Double Jump Upgrade 2->(Bonus if on a 100%, and the associated abilities and hearts)->FireMachine->Energy Boost 2 ("yellow energy") and now we can go anywhere.
On a 100%, I actually think it makes the most sense to do Curtain next. The reason is to activate the ghostly flowers quest as soon as possible (which would mean completing Curtain, turning round as soon as the save point on top of Curtain was activated, and doing the top of NightClimb, picking up the toughness boost along the way). The more areas visited with the quest active, the fewer need to be revisited to complete it. Apart from that, the order doesn't really matter; probably Lucky Pots would be the next thing to get, because with yellow energy all the items along there can be collected in one go, and it'd help with crystal grinding through the rest of the run (100% needs lots of crystals, and Lucky Pots + the already collected Magnetism makes them easy to collect along the way, rather than having to wait for boss drops).
Apart from having to do IceCastle before most of Skylands, and the LongBeach cutscene before BlackCastle (not that you'd want to go to BlackCastle with insufficient orbs on a speedrun anyway), it's now possible to go absolutely anywhere on the map, so the order should simply be picked to minimize backtracking (trying to activate the closest save point to something before going there, and not teleporting at all unless it saves time).
On the subject of crystals: I've been wondering about the fastest way to grind them, if there aren't enough "naturally" from bosses, and enemies and pots that are in the way that can be shot. Killing enemies is a moderately fast way to pull it off without exploits in realtime; Blancland is a nice spot, and can farm crystals quite quickly. TASes can make use of the gambling games, blackjack or Bonus, but they're quite slow (100 and 60 crystals per win respectively, and winning can take a while). Alternatively, you can make use of the fact that crystal count doesn't reset upon resetting to get the crystal drops from a boss multiple times; you'd want a boss close to a save point, who can be beaten quickly, who drops a lot of crystals. (Fluffy fits the first and third criteria, not so much the second.) Sadly, chests don't drop their crystals again across resets; I am, however, wondering if Rainbowdive does (in which case doing it a few times to get the 400 crystal reward that can normally only be collected once would be a very fast way to grind crystals.) I guess only the 100% run is at risk of not having enough (it needs to buy five hearts, two blue orbs, one gold orb, and a whole bunch of otherwise useless room decorations to get at the three minigames that give hearts for beating their high scores).
I guess for 100% planning, the next step is to put every upgrade onto the route somewhere, which could be quite a task, and deciding upon the details, especially orb collection at the end.