.flow is a yume nikki fangame developed by lolrust in 2009, with it's most recent update being in 2019, it's one of the most popular (and oldest) YN fangames together with yume 2kki, many consider it up to par with the original, if not better. Because of that, I tend to think of it as being an alternative experience with a much darker tone.

Despite what many say, I don't see yume nikki as a horror game, the furthest it goes is establishing an unsettling atmosphere in *some* areas (and uboa I guess) but for the majority of the time I find "dreamlike" to be a far better description. .flow on the other hand, while still not outright scary, definitely leans more on horror elements. Gore, rust and decay are prominently featured in many areas, there's many more macabre set pieces, body horror is something lolrust has knack for.

From the nexus you're only given 4 worlds to explore, as opposed to YN's 12, even still the games' worlds are around the same in scale and if anything, it might make .flow's easier to navigate, on my first playthrough I only needed to consolidate a guide to locate the last effect.
I'd still recommend you look up where to find the speed effect, unless you're really patient.

Download links on the .flow wiki lolrust's website Wiki page on where to find the speed effect