I think I got to 617 on my last run. It was a little easier after I found out you could hit the walls without dying. At first I thought the keyboard controls felt touchy, but they helps you get out of tight spots.
I happened to have a 1080p monitor in portrait mode so the webplayer size was okay, but it would be a better idea to shrink it to max 600 pixels high. There are lots of stupid laptops with low-DPI 1366x768 displays out there. Changing the resolution is super easy: just edit the index.html file Unity exports. You'll see the webplayer size in there near the top.
The visuals were really nice! Good palette, cohesive style.
Consider adding a downloadable Linux build. The webplayer isn't available for Linux.
Good to see another Unity 2D entry. =)
-mildmojo