With that kind of an enigmatic title screen I was expecting a game of Castelvania or at least Castle of Dragon grandeur. I'm utterly dissapointed...
You overdid the difficulty on that first boss batlle. Killed him 4 or 5 times and still not done? What's the point? Aoart from this, it is an outstanding game. Like the 8 bit programming and sound effects. The controls are spot on! Very well done!
I think the controls need to be better. Using the same keys to move and to aim is very clunky. These kinds of games usually use the mouse to aim and shoot on the computer. I know that's not contra style if you're gonna be religious about it, but it just works better and it's something of a standard in flash games.
The movement keys feel a bit slippery too. If you aren't going to do any precise platforming that can probably slide, but in a platformer, slippy controls always seem to make the game feel lower quality. At least, it does to me, lol.
I'd work on level design too. Right now it feels a bit blocky. This can add to the controls feeling off, so I'm not completely sure which one is most to blame. Just try to think of level design rhythmically. You should be able to run and jump very smoothly without stopping some direction of movement. If you do it right it'll feel like all the platforms just end up in the right places.
The graphics and the music is nice enough. If you tighten up the gameplay a bit it could be decent.
Eh it was fine but I didn't overly enjoy it.
Thats how flash games should be :D