This use of the code is a clear legal breach of copyright, in the absence of specific agreement with the copyright holder.
(On the Hatetris page, the author declines someone’s request to use the code elsewhere)
License: MIT
The reason you're getting so many down votes is because you made strong claims in a harsh tone that turned out to be false in a trivially verifiable manner. The intent there is that you should've verified your claim through and through before attributing a misdeed to someone who simply sought to share something they thought was cool to make with others.
The sibling points about trademark law (which is different) and remix culture (which has some legal protection but not that I’m aware for lines of code) seem to miss this point.
This is a licensed use, it turns out, which is great. If the author here had not identified that before publishing, then they were putting themselves at legal risk.
[on a technicality, the MIT license hasn’t been properly invoked, since the MIT license requires the text of the license to be included in full, but the original author’s consent for use seems now to be clear]
Legally though, just because one person's proprietary work relies upon another person's proprietary work, doesn't mean it suddenly becomes open source or public domain.
This “Lovetris” work is a blatant copying and republishing of someone else’s proprietary work effort with no permission. Morally, I don’t see this as an egregious abuse, but I can see why this community would object to someone not acting in the spirit of open source licensing.