I'll try it. I must admit that I haven't used J1E yet. I'll find a peaceful evening to look into J1E and try this modding!

Over the past days, I've remembered several new version differences that aren't yet on versions.html. They're all missing hidden springs:

• Diamondus 2: 1.0 and 1.3 have at least 4 hidden springs scattered near the top of the level. Good-1.2 doesn't have those springs.
• Tubelectric 1: After the longest pipe ride, before the half-way checkpoint signpost, there is a large room. 1.0 and 1.3 have at least one hidden spring on a floating platform in this room. Good-1.2 doesn't have that spring.
• Exoticus 1: Has a hidden spring in 1.3, but not in 1.2, on the purple bricks near the half-way checkpoint signpost.

I'll see what happens if I put the 1.3 levels into good-1.2. And I'll update versions.html.

We should also consider the legal issues:

• If we base this project on 1.3 executables and levels, we'll have to mod levels, but never copy anything from other versions. What GOG ships is entirely sufficient as a base; the modifications can be any permissible license or public domain.
• If we base this on good-1.2 executables, we must mix files from at least two different versions. What legal basis exists for us/GOG/anybody to extract and have GOG ship parts from 1.2? GOG is probably licensed to sell the 1.3 only. But the result will be shipped to thousands of players worldwide.

Ideally, we'll get in touch with GOG directly on these issues. I'm happy to do it, but I need a contact first. Merely writing to customer support won't cut it, I tried this for Orbitus 2 in 2018 and got no reply. I'll need a hands-on contact who realizes the importance and subtleties of what we do here. Maybe via VioletCLM?

Of course, there is the chance that I overthink this, given that Epic likely hasn't played through their own version in 25 years, not even before re-releasing in 2017. :-P

-- Simon