Overall a pretty good game but there are a few issues that make playing past the first boss a bit too difficult, but I'm sure they are small issues to fix.
The main problem is that levels are not reset correctly are thus in some configurations it becomes impossible to catch a moving line without exiting the line (I gave up after spending 15 minutes on 2.6 unfortunately) which is thus unfair and can irritate the player.
For the levels, you can figure out easily what each thing does which is good. One of the problem is the amount of requirement to complete a level : get all the keys, have > 80% and not exiting the line more than a given number of times. It makes it hard to keep track of everything. Maybe having some levels with or without some requirements would have been nice.
The boss fight is pretty cool, but I'm wondering if it was really necessary. I mean I know you love including bosses in your games but because of that, you introduced a dmg/def up/down mechanics in the level that the player won't really understand before he has fought a boss, which is a bit counter intuitive.
Graphics-wise, the simplicity and juiciness of the top part of the screen is not too coherent with the more classical and detailed bottom part. But I guess it's just a matter of taste.
Sounds-wise, everything is good, and I like that you did some sounds with your voice.
Once refined and simplified a little bit, it would make a great game for tablets and smartphones!