The high ratio for this one really isn't as difficult as you'd think. There's just some trick to grinding it out that might make it seem harder than it is.
In general, play the earlier levels. Using Morpheus, you can generally beat the first few levels with a very smart colorgun usage to not have to worry about a fast moving final enemy. This means just save up your "Thumbs Up" until you have a spotlight and then when you can clear the level with 1 or 2 of those shots, use it and end the level.
Here's the part you have to watch out for:
You can't restart from Level 1 until you at least cleared the boss of World 1. I had my tracker on and noticed that it wasn't going up when I just did the first few levels and restarted. After clearing the first boss however, you technically have a save game which can be restarted. This isn't completely a bad thing, as going for the fast clear of World 1 (sub 7 minutes) will likely take numerous attempts.