NeoLemmix is an upgraded version of the Lemmix engine, which fixes the glitches carried over from DOS Lemmings, and adds many new features. Essentially, it is an attempt to bring Lemmix on par with other modern Lemmings clones such as SuperLemmini and Lix, while retaining the traditional Lemmings feel to a larger degree than they do; this is why it is based off the existing engine rather than being built from scratch.
You can download the NeoLemmix engine here.
Download NeoLemmix (V10.12.14)
Note: If you intend to download the level editor too, it comes with a copy of the engine, so you don't need to download that here.
NeoLemmix is only available for Windows, but should be possible to run on Linux via WINE. Please note that fullscreen mode is known to not work on certain Linux desktop environments (such as Ubuntu's default environment Unity).
The older version naming scheme of X.YY-Z has been retired. This is why, if using V1.48-B or lower, the update check will report "V1.48n-C" as the latest version available even though no such version exists in practice.
Need an older version? Here are the older versions that are available:
Note to users of Avast! Antivirus: Avast has a very bad history of causing problems with NeoLemmix, including preventing deleting / updating NeoLemmix, or in some cases preventing being able to play it at all. You may be able to get around this with changing Avast!'s settings, but I would recommend if possible, use a PC that has a different antivirus. (Other free options include AVG or Comodo.)
NeoLemmix does contain a lot of new gameplay features. An excellent way to familiarize yourself with them is to play the NeoLemmix Introduction Pack:
Download NeoLemmix Introduction Pack
If you want to play the official games on NeoLemmix, you can get them here. There is a currently-in-progress project to create a "Lemmings Redux" pack, using selected levels from the official games with fixes, better NeoLemmix-ization and an improved difficulty curve, to offer the best experience to new players of Lemmings, or those replaying after a long break from the game.
Don't like the Amiga musics? Download one of these music packs! Extract them to a subfolder called "music" in your player's folder.
Download Original Lemmings DOS Music Pack
Download Original Lemmings DOS Special Graphics Levels Music Pack
Download Original Lemmings Acorn Music Pack
Download Original Lemmings Sega Genesis Music Pack
Download Original Lemmings Sega Master System Music Pack
Download Oh No! More Lemmings! DOS Music Pack
Initially, NeoLemmix started out as merely a project to fix the bugs and nothing more, but eventually gained more and more new features. The NeoLemmix engine evolved from the version of the Lemmix Player used in the now-retired Lemmings Plus II Bonus Pack, and as such a lot of Lemmings Plus II and Lemmings Plus II Bonus Pack's unique features, such as secret levels and gimmicks, became part of the NeoLemmix feature set. Although NeoLemmix versions of the official game Lemmix Players, and the old Lemmings Plus packs, had been available for a while, Lemmings Plus III was the first content to be developed specifically for NeoLemmix and thus show off most of its capabilities at the time (although it must be said that Lemmings Plus III uses very little of what's now available in NeoLemmix, due to new features being added since its release).
Of course, expanded features require an editor capable of supporting them. In the earliest days, the only option was to use a traditional editor, then use a text-based program called "QuikEdit" (or a hex editor) to adjust positionings and implement NeoLemmix-specific features. Later on, NeoLemEdit was developed, which was essentially a Windows-based remake of LemEdit with full (at the time) NeoLemmix support. Eventually, the source code for the original Lemmix editor surfaced, and thus began the development of the NeoLemmix Editor based on that. In addition to supporting traditional formats and NeoLemmix, the NeoLemmix Editor also for some time implemented support for SuperLemmini, which was an upgrade to Lemmini in a similar vein to how NeoLemmix was an upgrade to Lemmix; although recent versions of the editor no longer support SuperLemmini.
Note that other engines generally cannot load NeoLemmix level files. SuperLemmini can load some NeoLemmix levels, but is limited by the fact that it doesn't support many of NeoLemmix's features.