I love feedback like this! My brother (the artist) was happy to hear you say you liked the art. I'm really glad you mentioned the Mac version not working, because formerly I knew nothing of how a Unity game worked on Mac. Now I can look into this problem and hopefully prevent it next time. Also still got to figure out how to get the browser build to stop breaking, because for now it's pretty much a toss up every time I make a WebGL build.
In any case, we're really glad you enjoyed the game. And now that you mention it, I see how selecting the next level with a mouse, especially in a game with levels as short as these, would detract from the overall gameplay. Which is why I'm glad you said it, so in the next jam I'll know make a more efficient system, most likely just transitioning automatically like you said.
So thanks so much for this feedback, it's one of the things that makes game jams so invaluable.