Update: I played using Firefox (normally I play using Chrome) and while the performance was _much_ worse (the game ran noticeably slower, and the UI was only registering clicks 50% of the time), I actually got much further.
With Chrome I think the max tick I reached was ~24k, while with Firefox I got to 38k on my first attempt.
I'm not sure if the actual behaviour was different, or just the slower UI gave me more time to react and plan better. But certainly there's a difference.