Made 100% in pen, just to show @notzach how at least I think the pen games are made. Once you start to understand how the blocks fit, everything can become fairly efficient. An interesting thing to note is that it doesn't seem to lag much even with insane numbers of "objects." I got it to about 700 bullets on screen at once before I started getting lag. NOT AN ACTUAL GAME for now at least, I need to test collision detecting as well.
I mean, this isn't an original idea by any means. I just wanted to see if I could create this. Only one sprite and it's all in pen. The costume doesn't show up. Being in pen, this can be really flexible. If you'd like, try editing how the bullet or player looks and see how that turns out.