[SUG][CONTENT] Diagonal one-way arrows

[Strato Incendus]

Since we have a currently-ongoing debate about changing the appearance of one-way arrows, now seems like an appropriate time to bring this up:

While trying to fix backroutes to my levels, I repeatedly ran into the issue that there is no type of one-way arrow that allows a Miner to pass, but not a Digger - and vice versa. This pretty much solely boils down to the fact that horizontal one-way arrows can still be dug into (as predicated by the original Lemmings rules, which shouldn't be altered), whereas downward arrows are more strict, reliably preventing Bashers from passing through them. In other words, horizontal arrows only point towards the one side from which you cannot remove the terrain, whereas vertical arrows (both downward and upward) indicate the direction in which you have to move with the destructive skill.

Now, since downward arrows have been around for ages, I don't think their behaviour should be altered either - thus, it would still be impossible to create terrain that allows Diggers to pass, but not Miners.

However, what we could create is a type of one-way arrow that allows Miners to pass, but not Diggers.

You guessed it: I'm talking about diagonal one-way arrows!

In order to make these more universally useful, I'd make them a little less limited, with the arrows actually pointing in both directions, but at an angle. Moving diagonally along this trajectory would be possible, whereas moving along the opposite diagonal line would not be. Straight vertical or horizontal movement through this terrain would of course also be impossible.

As such, diagonal arrows would allow both Miners and Fencers to pass, but only from opposing sides - e.g. a Fencer from the bottom left or a Miner from the top right, but not a Fencer from the right or a Miner from the left. And then vice versa for diagonal arrows in the opposite direction.

Now, obviously, there are many cases in which you want terrain to be Miner-friendly, but not Fencer-friendly - or vice versa. This is usually one of the most critical steps to enforce whether lemmings can pass through a chunk of terrain only from above or only from below.

And this takes us to the question whether several different types of one-way arrows can be stacked. (I haven't actually tried this yet.)

If this is the case, then you could already create unidirectional Miner terrain right now, by stacking downward arrows with horizontal arrows: The downward arrows would prevent bashing and fencing, while the horizontal arrows would force the Miner into one direction only. Diggers could still pass through both unaffected.

Now, if the same logic were applied to diagonal arrows, you could indeed create Miner- and Fencer-exclusive terrain by stacking vertical arrows with diagonal ones: The diagonal arrows would limit the terrain to being removed by either Fencers or Miners only - and now, depending on whether you have upward or downward arrows stacked onto them, you could limit the area to only Miners or only Fencers specifically.


In general, I think the ability of Diggers to bypass any type of one-way arrows, except explicitly for upward ones, is a massive loophole that can easily be exploited for backroutes, independent of the setup of the individual level.

Therefore, we could really use a tool to rein in the Digger.

[namida]

And this takes us to the question whether several different types of one-way arrows can be stacked. (I haven't actually tried this yet.)

What will happen here depends on which version of NL. V1.43, one will overwrite the other (not sure what the priority order is). At some point between that and V12.0.0, this changes to "they will combine effects". It should be noted that neither of these are intended behaviours, but rather are bugs. Therefore, there is no guarantee they will always work exactly as expected.

V12.7.0 finally fixes this and introduces a defined, intentional behaviour: When two different directions of one-way arrows overlap (it must be different directions, not just different objects but same direction), they cancel out completely - both physics-wise and visually. The area where they overlap just becomes normal terrain, with no arrows drawn onto it. At the time that this came up, I mentioned that diagonal arrows could be considered as a dedicated feature, but that they'd have to be an intentional dedicated feature, not a side effect of using the arrows in an unintended way.

So yeah - if there's enough interest and enough puzzle potential, these could happen. I'd need to see some examples of where this would be useful, specifically in cases where alternative methods of setting up a digger-proof OWW (such as by having steel or empty space in the corners so that it must be handled at an angle) is either not feasible or has too-severe impacts on a level's visuals; but I'm open to the idea in general. We'd also need to discuss exactly what each direction means.

[Strato Incendus]

At the time that this came up, I mentioned that diagonal arrows could be considered as a dedicated feature, but that they'd have to be an intentional dedicated feature, not a side effect of using the arrows in an unintended way.

Good to know you already came up with this independently of me! I must have missed that.

I'd need to see some examples of where this would be useful, specifically in cases where alternative methods of setting up a digger-proof OWW (such as by having steel or empty space in the corners so that it must be handled at an angle) is either not feasible or has too-severe impacts on a level's visuals

Digger-proof by itself is not the problem - both steel and upward arrows do the trick perfectly fine. The problem is "Digger-proof, but not Miner-proof": There is nothing that will allow a Miner to pass that won't also allow a Digger to pass. Miners by definition move down and horizontally, and both horizontal and downward arrows can be removed by Diggers.

The opposite situation - Miner-proof, but not Digger-proof - can only be achieved with horizontal arrows pointing into the opposite direction than the one in which the Miner would want to go. As such, this terrain is also not completely Miner-proof, but only in one direction.

Note that I'm mainly referring to continuous chunks of terrain here, since those are usually the ones most in need of treatment with one-way arrows anyway: Continuous chunks of terrain are the most vulnerable to backroutes based on destructive skills, just like large empty spaces in a level are the most vulnerable to backroutes based on creative skills.



Since my motivation for opening this thread was fixing backroutes in my levels (specifically from playtesting of Lemmings Open Air), I'll happily provide some examples from that pack! For the sake of simplicity, I'll just copy and paste my responses to the replays that showed me the necessity for diagonal arrows.

Lemmings Open Air

Soft 22, "No roots": I wouldn't call this a "backroot" , as anticipated, but the intended solution uses two worker lemmings from opposing sides, rather than just one. I don't see a way of enforcing this, though, because you basically just used a Digger in place of a Miner, giving the platformer an easier time. But there is no way to make a piece of terrain Miner-friendly but not Digger-friendly - downward arrows allow for both, and horizontal arrows do as well (they don't prevent skills going through them at a 90-degrees angle, in contrast to vertical arrows). So this level will stay as it is, for the time being.

Hardcore 03, "The descent of Lem": Almost intended. Bouncing the Miner of several Blockers is the important part. However, you created a shortcut when you cancelled the Miner by digging straight down at the end. Then again, there are no one-way arrows that can stop Diggers but allow Miners to pass through. Steel can work by forcing the path to "curve" around it, but steel can also be easily abused to cancel Miners that aren't supposed to be cancelled.

The problem with steel is also that, while it can block paths on the one hand (in this case, most importantly, for Diggers), it can also easily be abused to cancel skills. This is an actual gameplay issue, aside from the cosmetic drawbacks that steel and one-way arrows can cause, as you already mentioned.

Let's say you have a piece of terrain which is supposed to be removed by a Miner. You add steel to it to prevent vertical shortcuts with Diggers. However, the question of how to cancel the Miner is supposed to be one of the main challenges of your level. Maybe you want to bounce it off a Blocker; maybe you want to Clone it. Maybe the Miner is just supposed to be cancelled, but do you need a Bomber, Walker, Builder, Platformer, or Shimmier to do it? Or do you need to (infamously) cancel the Miner with a Miner in the opposite direction? These are great layers of entropy to add to a level.

In all of these cases, the Miner should definitely not be allowed to simply tank on steel, after which you could comfortable assign another skill facing in the opposite direction.

The only way I can achieve this so far is through on-terrain fire traps instead of steel - they still prevent passage, but also don't allow for skill-cancelling abuse. In those cases, you also have to set them to "no overwrite", lest they become hidden traps inside the terrain. Depending on your level design, on-terrain fire traps might look even more stupid than steel or one-way arrows - but if they're the only thing that can enforce the solution on a mechanical level, what else should you do?

Diagonal arrows, in contrast, would safely prevent the Digger from going through, while at the same time not providing the Miner an option to cancel himself.

Since they would allow both downward and upward movement along their diagonal line, the only way a Miner could tank on one-way arrows (which then act like steel) would be if he suddenly ran into diagonal arrows at 90 degrees to his trajectory. Meaning: If the arrows at a lower altitude on the terrain pointed into the opposite direction than the upper ones.

[namida]

It doesn't seem there's much interest in this idea. If I'm wrong, and people just haven't been speaking up, speak up now - otherwise I'll assume this is an idea without much interest, and reject it now.

[Proxima]

I'm against this. It's already confusing, having to remember the properties of horizontal, down and up arrows, which are not easily predicted from each other; diagonal arrows would add another layer of confusion and would only be helpful very occasionally.

[Strato Incendus]

As I said, my main point for diagonal OWs is that the Digger can currently bypass all OWs except for vertical ones (which also stop the Miner, so they don't help that much).

I don't understand namida's point about steel or empty space in the corners? Such obstacles in the corners won't stop the Digger from going through the middle. And if you put steel or empty space in the middle, that in turn can also easily stop a Miner when trying to go through this piece of terrain at an angle.

[Proxima]

Something like this, where S is steel and W is wall:

Code Select Expand

SSSSSWW
WWWWWWW
WWWWWWW
WWWWWWW
WWSSSSS

[Strato Incendus]

Thanks for the explanation, Proxima!

Indeed I have used such a structure on my Pit Lems level "Making your mine up".

The problem is that steel can be abused to cancel Miners. There may be opportunities where you want to enforce the use of a Miner rather than a Digger, but without providing an easy way of cancelling that Miner once it has been assigned.

The only way for me to work around this cancelling effect was to additionally cover the edges of those steel pieces with on-terrain fire objects... but that's kind of fiddly and ugly at the same time.

[Proxima]

Since the top steel restricts where you can start the miner, it would be possible to prevent a miner hitting the bottom steel -- though I can see that depending on the specifics of the level, that might not always be viable.