Pretty fun, completed the challenge with just under a minute to spare after 2 failed attempts so I'd say it's balanced well enough.
A fullscreen option would've been nice, though, since when I zoom into the page the top-right page UI covers a bit of the screen, though it's at least a useless part. The background of the game matching with the page made it hard to tell where the edge of the screen is and non-black colors are a bit garish for such a high amount of screen coverage, though I appreciate the customization option.