This game is pretty much at the level of Undertale / Deltarune in both length and quality!!! For me, it was like reading a captivating book that I could not put down for hours. An experience I last really had while reading Harry Potter books for the first time.
Although the description currently says that 4 hours is the expected time to get to the true ending, it might take you around 6 or 7 hours if you like to explore many possibilities like I do. And even after those 7 hours, there will very likely be many secrets you missed or only half-uncovered, and you could be tempted to go back and have a look. You should expect a world and story that have your imagination run wild with theories!
For the record, I played on MacOS, and it was no problem at all to immediately get rid of the gatekeeper block currently mentioned in the description. While actually playing the game, I encountered virtually no issues.
(P.S., I am a pianist, and this soundtrack seems worth playing for me! And that's something I only say for the catchiest game music I come across.)