The second ONML track reminds me of this sketch... 

If forced to choose at knifepoint, I'd take the 6 standard ONML tracks over the 16 new ones, but it's still a cool find nevertheless. In particular, the ones with more than four looped bars of music are pretty good.

Intriguing. While I don't actually have an original Archimedes, I -do- have a whitebox StrongARM machine sitting in my spares cupboard which runs RiscOS 4 and MarsQuake pretty well. This thread has motivated me to hook it up and throw Lemmings/ONML at it.

I must say, this is a pretty sweet Lemmings engine. No idea how much Clickteam have changed since MMF1, but it must've been substantial considering this was possible to make in a couple of weeks. Can't say I'm the biggest fan of the SNES version of the game though (especially the music).

One problem, I can't seem to get past the success screen following Level 1. A shame, I'd like to see how all the other skills are implemented. The MMF I know would wet its pants in fear at the sound of pixel-level graphic operations and collision detection.

If I recall correctly, the GROUNDxO.DAT files have four palettes in them; one used for the preview screen and one used during the game for both EGA and VGA.

The extractor script I wrote for Tundra lets you export PNGs of all the graphics using whatever colour scheme you want. Unfortunately, since it was released the Python guys deprecated the XML SAX library the game uses for just about frigging everything, and because of all the wide-eyed (read: crap) design decisions, I have little interest in touching the code without the aid of a long pointed stick.

That said, here's a stripped down version of the script I used. Go get Python 2.6 and PIL, then download this package. Extract it somewhere, then run the Python interpreter and type in the following:

>>> import os
>>> os.chdir("c:\\path\\to\\where\\you\\put\\lemresgrab\\")
>>> from decrunchedit import *
>>> fullAuto("c:\\path\\to\\lemmings1\\", PALETTE)

     (where PALETTE is one of "ega", "ega_prev", "vga", "vga_prev")

>>> fullAutoONML("c:\\path\\to\\onml\\", PALETTE)

This will dump all of the Lemmings graphics as PNGs into the included "style" folder. Hope this helps.

(For the two people that care, the Tundra site has been dead due to my ultra-reliable webhost repasswording my SQL database every two weeks I just finished my thesis, so next project is to port LemmingsDS to the N900...)

That's a pretty good list of things that need doing. However, it requires a little bit of thought to properly break it down into classes. Let's assume for now, you intend to make a reasonable first step: a demo which spawns a stream of lemmings which then wander about one screen of sculpted terrain. Like the original, assume everything is done at the pixel level.

Intro screen
Level cards
Victory/failure cards

These are among the last things you'll be doing. Don't worry about these.

Level initialisation

Let's say your prototype takes a single level name as an argument.
When your program first runs, it constructs a GameState object called gs.
It then calls the gs.LoadLevel("name") method. This method should do something like the following:
 - Try to load the level data from disk and parse it into a Level data structure
 - Check which GraphicsSet the Level uses, and try to load the GraphicsSet pieces into video memory
 - Create one large graphics buffer of the whole level and paint it with GraphicsSet pieces according to the Level terrain placement info.
 - Create some sort of clever hashing mechanism for collisions based on the Level info (e.g. terrain, exits, water, traps)
After that, you can call a method such as gs.Step() (update the lemming positions) followed by gs.Paint() (write changes to the screen). This, of course, has to be repeated for every single frame.

Level completion

This happens when you run out of lemmings and you're no longer inserting new ones. At this point, your game loop should stop.

Lemming state

You have a Lemming object for each lemming, stored in the GameState object. Each Lemming will be of a certain state (walker, faller, builder) and will have a different per-frame movement behaviour based on that state.

Pick a skill

That's just input control. Worry about that later.

Assign a skill (if possible)

This is just changing the state of the chosen Lemming object and deducting one from the appropriate skill counter.

Skill implementation

This is done in your Lemming object as something which gets checked each frame. I think I figured out bits of the movement by cranking DOSBox down to 10 cycles and watching the freeze-frame edition of Lemmings. All you need to know for walking is:
- Collisions are measured at one pixel directly underneath the feet.
- If the ground ahead is between a -2 to +2 difference in height (making sure to check in the order 1,2,0,-1,-2), advance the lemming onto that bit of ground.
- Technically a lemming can jump up to 5 pixels in height, however you need to set an intermediate state called a bounder which advances up 2 pixels/frame so it doesn't look weird.
- Anything higher than 5, turn him around. Anything lower than -2, set him as a faller (which drop at a constant rate of 3 pixels/frame).

How Lemmings can affect terrain
How Lemmings can be affected by objects
Terrain collision

I can't really give advice about the best way to do collision detection, as the way I did it was pretty piss-poor (make a whole seperate RGBA copy of the level, with each of the 32 bits in each pixel representing terrain, steel, trap hotspots etc.).

Counters for skills, time remaining
Array for Lemmings

You keep the counters as variables in your GameState object. Same with your Lemmings, in an array or similar large data structure.

Lemming animation

Depends on the presentation backend you intend on using, but you'd want to load it in a globally-accessible cache much like your GraphicsSet. It's probably better for video memory to store animation in long strips, where each frame can be blitted from by using an offset and a common frame width. Lemmings is quite nice in the respect that each animation corresponds with a specific state.

What kills a Lemming, why

See collision detection. The lemming death animation is stored in the trap itself, so all you need is to make the lemming disappear and activate the trap.

Windows frontend
Mac OS X frontend

Again, these last guys depend on the language and presentation backend you intend on using. You mentioned C#; while I think it's easily the best thing Microsoft has ever made (the second, of course, being SkiFree. No, Chip's Challenge was phoned in from Epyx and doesn't count), using the provided graphics bindings (DirectX, XNA and friends) will kick you in the nuts if your plans are multiplatform. SDL.net might be worth a look, as that can (hopefully) run on Windows .NET and OSX/Linux Mono.

Nice hopefully this should mitigate all of the uncertainty surrounding the old forum.

Mr. K, please keep at your efforts to get a SQL dump of the old forum. Some of the stuff on there (such as file format information, dialogue from Mike Dailly, etc) is far too valuable to lose. Failing that, let us know in advance if you plan to kill the old one off permanently so we can run a quick-n-dirty HTML page-save effort. We're counting on you 

Gimme a week to finish exams/figure out the explosion-timing bug and v0.8 will be out. Promise.

(maybe I should start using subversion instead of thinking about it really hard)