This is great! And super hard!
It was completely unplayable for me with the default cursor speed, as it was impossible for me to move the cursor only one step at a time, but when I turned it down to 1 or 2 it worked great.
I wonder if it'd be possible to add mouse control, or if that'd make it too easy (navigating the cursor around with the keyboard does add its own challenge). But with mouse support and potentially a browser version for a lower barrier of entry, I think this could be a hit.