it's a flash game, more sprites on the screen = less FPS, your setup be DAMNED. game physically can't be fixed due to engine limitations. lowering the quality gives the engine some wiggle room, but it ain't much.

I vaguely remember something like this stopping me from completing the game.

Yeah, nothing much you can do other than wait for a fix or refund the game.

Thanks. I already tried that tutorial. I've discovered that after taking those 12 steps, they are not remembered the next time I start the game, and would have to repeat them every time. What a hassle that would be.

Looks like this is a known bug. Here's a tutorial which may fix this - https://steamcommunity.com/sharedfiles/filedetails/?id=260668911

That is weird for a low graphical game.