I really liked the idea, but I would tweak some values in code tho
1. I thing that the time when you can hit yellow particle is too short. For me I found it hard to sometimes run to the particle before it dies.
2. Not having to start everything from scratch every time you loose would be great. I think there should be an option to repeat only the level you failed.
3. The sword doesn't point directly at mouse cursor. At least on my machine there's around 45deg gap. It's a minor thing but still makes gameplay a bit harder so I would fix it.
Great game!