Glitches in Lemmings

[namida]

Do not look at NeoLemmix code as a reference for L1 physics in any way. NeoLemmix is a completely seperate engine which is intended to remove glitches, and targets custom content. Very little of the original Lemmix code remains, at any rate.

Instead, look at my modified versions (so-called "V29") of Lemmix here: https://www.neolemmix.com/?page=download_list&program=42 (Last download is the source code)

I believe another user here has made a few further fixes, using said source code as a starting point, too. EDIT: Yep, this is the topic you want to look at for that: https://www.lemmingsforums.net/index.php?topic=4973.0

[EricLang]

Thanks! I was wondering about the correctness of using the global "Paused" state of the game. method IncrementIteration().

[Gronkling]

On megadrive\genesis, if more than one bomber explodes on the exact same frame, only one of them will cause any change to the terrain, the others will blow up as if they're in a steel area.
(currently untested on other platforms)

[Minim]

Nice find! Fortunately this doesn't happen in LemmixPlayer, as the replay shows that terrain is destroyed from the two bombers with both lems dying. We've yet to see if this happens on DOS though.

(To perform this trick correctly, assign the second bomber on the second frame the 4 is shown in the countdown to allow a falling bomber to detonate at the same time as the walking bomber.)

[namida]

Nice find! Fortunately this doesn't happen in LemmixPlayer, as the replay shows that terrain is destroyed from the two bombers with both lems dying. We've yet to see if this happens on DOS though.

(To perform this trick correctly, assign the second bomber on the second frame the 4 is shown in the countdown to allow a falling bomber to detonate at the same time as the walking bomber.)

I spent some time earlier trying to reproduce it on actual DOS, as my gut feeling was that if it did happen on DOS, this would be one of those rare cases where Lemmix did not reproduce it accurately.

But no - this glitch does not happen on DOS (Amiga is untested, I'll leave that to someone else).

Video: https://www.youtube.com/watch?v=UX7fs4ORvfg

In particular note the fairly easy setup for it here - RR 74, then assign two consecutive lemmings bombers on the frame they spawn, and make sure the second one is falling when he explodes (but the first is not). This setup should allow for testing it on various other platforms, too.

[Simon]

Attached is another repro of DOS L1 with two simultaneous exploders, they produce two craters. Tested with exploder assignment during nuke.

-- Simon

[Gronkling]

Whilst I was setting up a recording of this glitch, I accidently found a DIFFERENT MD/genesis bomber glitch!
If a lemming explodes as it is falling below the level, it will play an oh-no sprite rather exploding instantly like a normal faller. In the video I do this one the first frame it occurs as it looks most impressive, however it works at any point below that too, and from greater heights.

Here's a video demonstrating both
https://www.youtube.com/watch?v=LT4P7Z9iDrA

[Zaphod77]

Pausing for time glitch as i understand it is that the timer that decides when the hatch opens still runs while the game is paused.

In Amiga, that timer doe stop when you pause.

But in DOS version, the "it's time to open the hatch" timer will still run when paused. so f you wait two seconds, the hatch will open immediately when you unpause.

the number of pauses doesn't matter. just whether any are before the hatch opens.

[Gronkling]

Builders are able to clip horizontally through walls when at the maximum height in the megadrive/genesis port

https://www.youtube.com/watch?v=u5pH1VL81ic

[The Tomato Watcher]

Alright. Maybe this one doesn't fit with the rest, since it's not really a physics-related glitch, but it's too interesting for me not to share, and after all, it is a glitch in Lemmings.

This one is on the Amstrad CPC version, and I call it the Cursor Glitch. The setup is rather specific but the execution is simple. Find or make a spot where a lemming is almost at or is going to the top of the level. The terrain can't go to the very top of the level, as it will act as a ceiling when climbing or building; it has to stop just before the top, so the lemming has just enough room to hoist or ascend. If you use the locking feature on this lemming, it should force the cursor out of bounds, or, if you're a couple pixels short, a digger or miner will nudge the cursor upwards (for some reason). Be sure to move your cursor or make sure the lemming dies before coming back onscreen or the glitch will end. You'll notice that the cursor is leaving a trail of ghost images all over the level at this point, and that you can't move it down (or possibly other directions, depending on the circumstances). These ghost images actually act as terrain, by the way. If you move the cursor directly upwards, it will reappear normally at the bottom of the screen and the glitch will be over. If you keep moving your cursor around out of bounds, you may cause some weirdness to happen. Move it in just the right way, mainly at the very top of the screen, and you will utterly break the game. Possible effects include ridiculous lemming counts, teleporting hatches and exits, ridiculously high time limits, missing or incorrect animations, severe graphical glitches, huge surpluses of skills, an infinite loop of binding your keys, and of course, crashing the game.

The effects depend on how you move the cursor, which skill or skills, if any, you assigned to the out of bounds lemming, whether you're playing on disk or tape, what level you're playing, and more. Below is a collection of examples of just what can happen with this glitch. They are all in Mayhem 1, but it looks like there are a few other levels where you can pull this off, one of which being Fun 13, where I got somewhat different results. I would NOT recommend watching the tape version examples if you have photosensitive epilepsy! There are many flashing lights in the form of severe graphical glitches and loading raster bars.

https://youtu.be/l8W28Gq_4-8

[AsahiNyan]

i dont know if some of these have been mentioned already, but they arent on the main post, so im assuming not.
so here is a BUNCH of stuff:

Dos

blocker
(arguable)
blockers will always to to the right after being freed, even if they where assigned a blocker while above no ground in a action that allows for a blocker to be applied. (works only in original Lemmings 1, none later)

xDestruction skill - blocker
blockers can be used to override the hitbox of steel, this will make it so that you can use bombers and any other destruction skill (basher, miner, digger) to destroy the steel if the lemming is within rage of the blocker

miner (correction)
the possition of the pin of the miner is 1px below the floor, but this is compensated for on inital asignment, therefor this can only be done on the second, and onward, mine strokes, the time duration for in this can be done without destroying terrain is one Q(*)

lemmings on top always walking
lemmings on the top of the screen always walk, meaning skills can be applied to them, a funny side effect is that they are stuck in the first frame of the animation

Q manipulation
if you line up lemmings in the correct Q(*)-update order (the order in which the lemmings enter the level, and the order in which the lemmings are updated within a Q(*))
this can be used to wallzip (slide glitch) 2px wide lemming groups with a 3px wall

Amiga
xDestruction skill - blocker amiga
see " xDestruction skill - blocker" on the dos version
amiga has the special in this case that the glitch works with all destruction skills except bombers.

miner (correction)
same as dos

lemmings on top always walking
same as dos

blocker
same as dos

Q manipulation
same as dos

Super Lemmini
all glitches on amiga except  xDestruction skill - blocker steel glitches, lemmings on top always walking, and blocker right-facing glitch

blocker
spamming blocker on a lemming on every Q(*) if the lemming's pin is not above ground the lemming will move down by 2lpx(t) (4px) on every Q(*)

half pixels
(arguable)
half pixels (1px, 0.5lpx(t)) can be used for percise things, they arent necessarly a glitch though

RPLS
RPLS is devided into 2 categories: RPLS, and RPLS99

RPLS: allowing all powers of RPLS with no limit
RPLS99: allowing all powers of RPLS with the exception of caping the RR at 99

RPLS is a glitch in which you manually edit a replay file to achive "infinit skills" and a rr up to 106, it is a incredibly powerful glitch that breaks every level ever made for SL if used on them.
ways of creating replay files:

manual rpl editing:
you can manually edit the replay files and type out what skills happen by hand, but this is very tedious and unoptimal

.ini editing:
you can copy the levels .ini file, edit the skills to be infinit in it, do the replay on  that and than change the replay code to direct to the original:
   edited level direction code example:

Code Select Expand

#REPLAY NEW
#FORMAT 1
#REVISION 0.104
#Players 1
#External Levels, 0, 0, Single Levels, You need bashers this time   
   direction to original example:

Code Select Expand

#REPLAY NEW
#FORMAT 1
#REVISION 0.104
#Players 1
#Lemmings, 0, 4, Fun, You need bashers this time
miner
in SL the miner is already below on initial assignment, SL also doesnt have a minimum amount of Q this can be done in as the miner is almost 1px below durring the entire mine duration, using this you can move downwards slowly without falling.

miner floor clip
similar to avoiding falling with the miner, if you Q(*) perfectly alternate between either: basher and miner or builder and miner you can clip through floor compleatly without destroying it

wallzip ("sliding glitch")
still the same 3lpx(t)-6lpx(t) (6px-12px)
3lpx in this version rather than 1Q jump time has 2Q just time (1.5lpx(t))
the other px amounts also have diffrent amount of jump time however those are less important in the general working of the glitch.

Q manipulation
same as dos/amiga
diffrence: more strict due to doubled pixels/smaller pixels


NL & SLX
NLWZ
nlwz is a wallzip done in neolemmix/superlemmix, these have the limitation that they will cut off instandly, however if you do them perfectly it is possible to clip into any terrain using them

FZ (slx only)
sup category of NLWZ, same concept but you use a freezer for the initial jump, this means you can jump on a 1px ledge. this glitch has been reported and will be patched in 2.8.3, it is only possible in 2.8.2 due to the previous versions having some slightly diffrent unfreeze physics aswell

2SC
you can clip 2px through stel, or any other terrain, using a NLWZ and a blocker to turn the lemming around while jumping, since the game wants to force the lemming out of the wall, but because the lemming has been turned around the game pushes him further in by 1px, if the wall is only 2px he'll clip through the other pixel too since the lemming checks wether there is a wall too high to jump on the next pixel rather than the one its on (fixed in SLX 2.8.3, working in NL (assuming since i havnt tested it yet)

BLCBAC
(arguable)
you can use a blocker while a basher is on the 3rd Q of a stroke to turn him around, finish the stroke, and free the blocker at the same time, this can be used in backroutes (ex: lemmings cranium curious 17)

BLCBSC
(arguable)
same as BLCBAC but if you manipulate the Q order of the lemmings the blocker can be applied on the 2nd Q of the stroke, this means you can do a basher staircase (BSC) with just a blocker and a basher (currently isnt used in a backroute)

SC (fixed on all)
you can repeatedly spam a shimier to clip through any ground, including steel, it has however been patched on both NL and SLX

Genesis/Mega Drive
xDestruction skills - blocker
same as dos

hitbox override
a hitbox of anything can be overwritten, even by one that is nothing, this means in some (one) level there can be a tiny cap in a hitbox, a example for this is the TAS strat on M12 where we use this to destroy the steel even without having any blockers to help
this might be possible on other versions too, like Dos and Amiga, but i personaly cant confirm this, but it seems to be fixed on SNES

*
a Q is the bundle of frames that make up a physics update, comming from "quad frame" term originated by japanese TASers such as ま横 (mayoko), and mochi. "Quad frame" stemming from the amount of frames it takes for one physics update on the NTSC snes versins (4f).

t
lpx is px devided by 2
px in SL is doubled due to hires, and double amount of Q(*)
lpx is largly there because its more visible than the tiny actual pixels in SL, which most of the time dont even play a role in a levels solution

[namida]

a Q is the bundle of frames that make up a physics update, comming from "quad frame" term originated by japanese TASers such as ま横 (mayoko), and mochi. "Quad frame" stemming from the amount of frames it takes for one physics update on the NTSC snes versins (4f).

I will note, you used this term in reference to NL, but NL doesn't do a "quad frame" type thing. It just directly has frames, with one physics update per frame, 17 frames per second.

Welcome to the forum, by the way!

[AsahiNyan]

Didnt know that NL worked that way, but i'd probably still refer to it as Q since its essentially the same, and Q is just a physics update, which can be 1f, in that case the two are the same but Q would still be a usable term imo. It came from "quad frame" for "4 frames" but it has more gone to just mean a physics update in general.

Thanks for the welcome!
i've already been here for some time, just changed display name

[AsahiNyan]

Might be known but also havnt seen it here.
On the SNES version there is a level code for Fun1, on the US version its "SRDTPTP", funnily enough, you get this code after beating Sunsoft 5, the last level of the game. (only tested this on US v1.1 but will probably work on JP and EU too. though the code would be diffrent, thats why i didnt test those)

[namida]

I don't know if you can ever see it in game, but codes exist for Fun 1 / Tame 1 / etc on the DOS versions too. Ages ago someone reverse engineered the algorithm that generates the codes and made these ones.