Well I think it's great
Not too long, not too short. Easy but hard. I like that it's not so easy it's laughable but it's not so hard you tear out your hair. I even managed to get the secret medal (without cheating) which is a great achievement for me. Heck I liked it so much I wrote a medal guide. If anyone's stuck just check out my (only) note. Great game, good music, I really like it. And I like how it fires at an angle when you go up/down. It really helped with the bosses (when you're stuck in a corner and have a second, maybe, to move around before he fires the next shot).