Yeah DosBox 0.65 has the graphics fine (whereas 0.70 has the graphics bug), so the issue was introduced with 0.7 and then fixed with a non-default mode again, as I see it.

Can't say anything about the music but in DosBox I have the graphical error as well. Never bothered to debug though.
My memory is faint, but I think at least in the floppy version the screens were okay on Dos.

Another level that is intended to make use of a physics peculiarity of Lix. Unfortunately, it's very precise at the moments.

There seems to be an issue with a macOS build. From the descriptions of macOS users:

It starts and opens a window, but which has only a black screen. The music plays and at least with ldc it segfaults.

Issue 381 on github

From the #lix log of 4th of Jan, 2019 (concerning Lix 0.9.24):

[11:24:47]    <tarzeau> i've got an up to date 10.14 mojave mac now... i shall retry?
[11:24:55]    <tarzeau> remember what i need to install with brew?
[11:25:55]    <SimonN> brew install ldc dub allegro enet
[...]
[11:30:09]    <tarzeau> uncaught exception when i run ./bin/lix but that's surely the releaseXDG
[11:30:27]    <tarzeau> rebuilding...
[11:31:19]    <tarzeau> now i get a window called Lix, which shows black, nothing else
[11:31:59]    <tarzeau> adding --build=release as in windows
[11:32:04]    <SimonN> what is your exact build command?
[11:32:20]    <tarzeau> now it's: HOME=. dub build --build=release -f --compiler=ldc2
[11:33:07]    <tarzeau> oh wow now ./bin/lix goes fullscreen
[11:33:10]    <tarzeau> staying black
[11:33:21]    <tarzeau> pressing esc: segmentation fault
[11:33:23]    <SimonN> yeah, release defaults to fullscreen
[11:34:03]    <SimonN> go into the segfault with a debugger
[...]
[11:52:11]    <SimonN> tarzeau: When you build Lix, dub outputs versions of other dub packages. What version is "allegro" in that output?
[11:54:08]    <tarzeau> allegro 4.0.4+5.2.0: building config "no-libs"
[11:54:15]    <tarzeau> maybe i should not have copied that dub packages from linux?
[11:54:47]    <SimonN> hmm, 4.0.4+5.2.0 is correct version.
[11:55:34]    * tarzeau drops HOME=. and rebuilds, removed all the *-n/ dirs too
[11:55:40]    <SimonN> Copying stuff from Linux: dub stores built binaries in .dub dir, thus the copying could cause problems. Delete ~/.dub/ and (lix)/.dub and then build.
[11:56:14]    <tarzeau> i've not taken any binaries, just the sources
[11:56:21]    <tarzeau> but will try as well...
[11:56:28]    <SimonN> ah, hm, then should work. But try anyway.
[11:57:17]    <tarzeau> all black... maybe it doesn't find data files?
[11:58:02]    <tarzeau> oh user/log.txt says
[11:58:06]    <SimonN> in dub.json, in "libs": [ ... ], between these square brackets, add this line including quotes and comma: "allegro_color",
[...]
[11:59:17]    <tarzeau> added and rebuilding...
[12:12:51]    <tarzeau> i can't find ~/.dub on macOS but i removed .dub
[12:13:06]    <SimonN> okay, hmm, I'm sure it'll be fine
[12:13:15]    <SimonN> did the rebuild do any good?
[12:15:33]    <tarzeau> but the icon appears when starting it
[12:15:36]    <tarzeau> in the dock
[12:15:43]    <tarzeau> black screen as always
[12:16:35]    <SimonN> okay. Remove `"allegro_color",` again, then `brew install dmd`, then build Lix with `--compiler=dmd`
[12:21:45]    <tarzeau> building...
[12:22:42]    <tarzeau> it also builds fine, however same black window
[12:22:54]    <tarzeau> i run ./bin/lix from the source unpacked tree
[12:23:13]    <tarzeau> however esc just exits, no segfaults
[...]
[12:56:37]    <SimonN> tarzeau: download the music: http://www.lixgame.com/dow/lix-music.zip -- extract in Lix's directory, then run the game again. Does music play during the black screen?
[13:02:25]    <tarzeau> back, i already have the music there
[13:02:31]    <tarzeau> let me make louder
[13:02:49]    <tarzeau> yep music plays
[13:06:41]    <SimonN> okay, hmmm, this is tricky then. Lix runs but doesn't display anything.
[13:08:02]    <tarzeau> ack
[13:08:06]    <tarzeau> do you use opengl?
[13:08:45]    <SimonN> Not directly. Via Allegro 5.
[13:09:43]    <SimonN> Okay, I have one abstruse idea.
[13:10:12]    <SimonN> Downgrade DAllegro5 bindings and add allegro_color back. I will instruct you how to do this.
[13:10:35]    <tarzeau> k
[13:11:51]    <SimonN> dub.json, line 13: Replace with: "allegro": "==4.0.3",
[13:12:28]    <SimonN> in line 21 or so, add new line: "allegro_color",
[13:12:40]    <SimonN> (all these times, the trailing commas are important)
[13:13:03]    <tarzeau> done
[13:13:14]    <SimonN> in dub.selection.json, replace line 4 with: "allegro": "4.0.3+5.2.0",
[13:13:34]    <tarzeau> done
[13:13:34]    <SimonN> then run: dub build --force --compiler=dmd
[13:13:47]    <tarzeau> running
[13:14:20]    <tarzeau> built, runs the same
[13:14:33]    <tarzeau> and it's the same windowed or fullscreen
[13:14:37]    <SimonN> i.e., black screen, music plays, and no image? hmm.
[13:14:42]    <tarzeau> yes
[13:14:46]    <SimonN> Okay, then I'm out of ideas
[13:15:22]    <tarzeau> https://www.google.ch/search?q=allegro5+macos+black+screen&oq=allegro5+macos+black+screen&aqs=chrome..69i57.5323j0j7&client=ubuntu&sourceid=chrome&ie=UTF-8
[13:15:23]    <SimonN> I didn't believe this would have helped anyway, but I would have slapped myself had it been the solution and had I not tried it.
[...]
[13:16:34]    <tarzeau> https://wiki.allegro.cc/index.php?title=Allegro_5_Tutorial/Displays ?
[13:16:49]    <tarzeau> al_flip_display(); needed?
[13:17:06]    <SimonN> yes, should be needed.
[13:17:07]    <tarzeau> i remember macOS (well cocoa) has different coordinate system
[13:17:25]    <SimonN> Allegro is an abstaction over any OS-specific stuff.
[13:17:48]    <SimonN> maybe run that example code and see if you get window
[13:17:51]    <tarzeau> https://github.com/liballeg/allegro5/issues/546
[13:18:00]    <tarzeau> single buffer?
[13:18:11]    <tarzeau> i don't know either. if you want me to retry, tell me
[13:18:47]    <tarzeau> this gh issue produces black display, works windows + linux
[13:20:10]    <SimonN> okay, no time. I think I double-buffer. My code is in src/hardware/display.d, public interface to that module is ALLEGRO_DISPLAY* display to get backbuffer to draw there, then void flip_display()

Why is it needed to vote for each rule separately?
Actually you can have an advantage when you're in a rule with a higher survival rate than the others, which doesn't seem to be justified.
Why not make one big mixed round with all the levels and then best 5 levels or so go in the next round?

The level That Pesky Gap seemed to have relied on old physics (variable SI?).
I made a variant of it which uses likely a completely different trick.

Solution to newer Bulldozer version.

When testing freshly build levels you have to save, go out of the editor and play the build level, which is rather tedious.
Furthermore with normal play all your solutions during testing get auto saved by default what e.g. Ramond finds annoying since it can clutter your replay folder.

Therefore a test play mode from inside the editor seems to be a reasonable feature.

(Corresponding discussion from IRC:
[17:10:03]    <Ramond__> one other thing maybe, while testing your own level the game will auto-save each of your successful attempts, it will clutter after a while
[...]
[18:25:10]    <Forestidia> The auto save feature is important.
[18:25:24]    <Forestidia> It can be turned off I think.
[18:26:14]    <Ramond__> yeah it is important for playing, but rather hindering during level testing
[18:26:33]    <Forestidia> But what is your suggestion?
[18:27:06]    <Ramond__> I don't really have any proper suggestion, it only felt a bit annoying to having to clean out the replays manually
[18:27:15]    <Ramond__> maybe someone else has a good idea
[18:27:16]    <Forestidia> okay
[18:27:44]    <Forestidia> You can Esc the level before you hit the save requirement.
[18:27:58]    <Forestidia> I often do that when testing.
[18:29:02]    <Ramond__> that's a possibility but still a slightly tedious workaround (always having to have that in mind)
[18:29:27]    <Forestidia> The thing is to have a replay for the final version is important for coverage.
[18:30:08]    <Ramond__> dunno if feasible but what if there's a way to directly go into a 'test play' mode from the editor (skipping going back to menu to select play) which is identical to the normal play mode except it won't auto-save? (can still be saved manually somehow)
[18:30:49]    <Forestidia> A test-play mode from inside the editor would be good for other reasons as well.
[18:31:28]    <Forestidia> Since it's then generally less tedious to test your level.
[18:31:44]    <Ramond__> yes
[18:31:51]    <Ramond__> though for some reason I thought it was intentionally left out
[18:32:14]    <Forestidia> I don't think so actually.
[18:32:27]    <Forestidia> But I don't know for sure.)