This does NOT include features that have been backported to a V12.10.X release. Features marked with (*) have not yet been backported to a stable V12.10 build, but have been backported in source code and will be included in the next V12.10.X update if it occurs.
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# New Features #
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> Custom postview jingles are now supported.
> Support has been added for resizable terrain.
> Title screen layout can be customized for each pack.
> When running a mass replay check, options are presented for organising replays based on results (or just in general).
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# User Interface #
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> Added an option to force the default lemming sprites.
> Added a "timer bypass" nuke, which when activated, inserts a Nuke action into the replay timed such that the first lemming will explode on the current frame. Note that this does not allow doing anything that is not already possible as it simply calculates the correct time and inserts the action into the replay.
> Clear physics mode highlights one-way terrain when moused over.
> Hatches now show the remaining lemming count when in clear physics mode, even if they are not lemming-limited. Zombie hatches do this even outside of CPM.
> Mass replay check draws attention to mismatches between the version of the level used to record the replay vs the one used to test it.
> Mass replay check marks replays which obtain a talisman.
> Much more customization is possible for replay filenames.
> NeoLemmix is now DPI-aware.
> Postview success / failure jingles are now merged into a single option instead of being set seperately.
> Skill panel zoom is now independent of level zoom.
> Zombie color in CPM has been tweaked.
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# Other Changes #
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> Lemming spritesets are now required to contain athlete and selected-lemming recoloring data. They are also required to contain neutral and zombie recoloring data, but only on levels that actually use the respective kinds of lemmings.
> Level version number is incremented by 1 when running Cleanse Levels.
> Resizable objects can specify a default size that's different from their base image size. (The new resizable terrain supports this too.)
> Selected skill outline is now in a PNG file (which can be customized by packs) rather than hardcoded.
> Water objects in all official styles (including orig_dirt_md and orig_sega) is vertically resizable. Default-height water still looks exactly the same as it did before except minor differences in the ohno_rock water.
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# Bug Fixes - Physics #
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> Fixed buggy behavior when a Climber encounters a Splitter.
> Fixed bug that allowed assignment of Shimmier to a Climber at the top of a ledge.
> Fixed difference in dive vs turnaround height for Swimmers based on whether or not they are also a Climber.
> Fixed inability for swimmers to descend out the bottom of water. (Debatable if this was actually a bug or not, but it's changed.)
> Fixed incorrect fall distance for swimmers.
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# Bug Fixes - Other #
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> Fixed bug where a no-overwrite entrance / exit with a limited count, the remaining lemming count would also be displayed behind terrain.
> Fixed, hopefully, the temp-freeze that occurs if leaving the menu screen while the update check file is downloading. Fingers crossed this one sticks.
> Fixed (to the extent possible) replay issues that arise when preplaced lemmings are reordered and/or cloners are inserted / deleted.
The "major feature" will be resizable terrain (https://www.lemmingsforums.net/index.php?topic=4207.0). (I have decided to delay the new skills until V12.12.)
There's a lot of other minor features / fixes that have been made too. See the changelog above for full list.