itch.io

I can't find it. Got a link?
This is the "abandoned account": https://x.com/nomnomnami

It does link to a website though: https://nomnomnami.com/

So there are two ways to finish this out, I think.

1) Typically, there is a "meta-rule" that every puzzle has one unique solution. This is rarely if ever broken, because a puzzle with multiple solutions doesn't technically contain enough information to be solved; it's usually very frustrating! So, if you ever find yourself in a perfectly symmetric puzzle state -- as here, where the remaining clues and relevant board is perfectly left-right symmetric -- then any choice you make must also reflect that symmetry.

In this case, if you pick the rightmost available cell on the bottom row, you must also pick the leftmost. But then it's impossible to make one single region of six cells when you've already spread them eight cells apart. Thus, you must exclude the rightmost cell (and therefore also the leftmost cell).

2) I distinguish "lookahead" from "guessing" if I can see a contradiction in at most one step. Usually, it takes me some time in "lookahead" before I learn and recognize a new rule of inference; the rule is just a shortcut for recognizing when that type of contradiction would appear again.

In this case, if you pick the rightmost available cell on the lower line, you can quickly see that the two remaining 1-cell groups on the upper line must both be on the left side of the puzzle. That is, they must be touching, and thus not two 1-cells at all, but a single 2-cell. This contradicts their row clue, and so is impossible.

The key here is really to play the 1-1 clue on the upper line against the 6-clue on the lower line. Only one arrangement of the 6 makes a 1-1 arrangement even possible. Once you have the strategy of playing one group against another like this, it stops looking like "guessing" and starts looking like "checking constraints".

Personally, I think (2) is the "morally correct" reasoning; but having (1) in your back pocket can help focus your attention, even if you don't use it to make progress!