I'd like to welcome you to the world of Nightcore:

https://www.youtube.com/results?search_query=nightcore

But in more seriousness, a song is normally quite distinguishable from another song than a tetris implementation from another tetris implementation. Conceptually, having a normal tetris vs having a tetris give you the worst solution (hatris) is the same jump as having a normal tetris vs having a tetris give you the best solution (lovetris). IMHO it's not the code itself what makes a "new thing new", it's the concept behind it.

I completely disagree. I made a hatetris myself (called Lövetris) once, spent a good 20 hours on it. If someone took it, flipped a sign (or even re-skinned it) and published it as “by” them I’d be furious.

Yes, the product would be different, but 99.9% (literally) of the work would still be mine. The hard part is building the app, not changing a parameter. I wouldn’t even call that a “remix”.

That seems the opposite of open source thinking, which might be why you didn't published it and why you think that way. As an open source author myself I see this as a fair move. Just different opinions :)

"The hard part is building the app, not changing a parameter" that really depends, why didn't you take an open source implementation yourself and built on top of it? Then it wouldn't be "as hard", would it? If you want to go the hard road that's totally fine, but it's not fair to say that because you go that road you deserve something that someone else got easier using pre-existing technology. Also there's literally dozens of famous examples in science and medicine when the hard part is changing a parameter and saving millions of lives.

Also, I’m not saying it’s a problem to tweak someone’s open source project, I only take issue with presenting it as your own, with such a minimal change.

If you want attribution, require it in the licence.

Maybe I’m not being clear. I’m talking about _etiquette_. Not licenses or laws.

I don’t know if there are open source hatetris available, but in my case it was an assignment so that wasn’t an option.

If i build something from scratch it doesn’t really matter that it “could have been” built on open source. And in any case, it might be perfectly legal and in accordance with the license to do what OP did, I’m just saying it’s bad form. Making a minor tweak doesn’t make it “by you”. It just doesn’t.

And this is not medicine and lovetris doesn’t save any lives, so I’m bot sure it’s relevant.

Did you give an open source license to your project? I think some licenses have better attribution requirements than others.

I didn’t publish it at all, I’m just thinking hypothetically here!

Good idea! If more thought hypothetically about the consequences of various licenses I think it would be a good thing.

In retrospect some of my projects might have more liberal WTFPL on them where I really don't care if someone else said they did it, but others I would want more recognition and more copy left for their changes. (I think some of my bigger projects side with the copy left and the smaller with the liberal.)