haha Money shot. Indeed.
Anyway,
here's a new demo. One level is fully playable, incredibly underpowered boss and all. Hopefully it's a bit more varied now. I still get bored playing it, which is a bad sign, but I can't pinpoint why. I may add obstacles that force the player to jump around a bit or something. And new levels with new scenery/enemies might help.

I've been following your game. You seem to be taking great steps into making the gameplay more varied. I think the problem with boredom may be that, in the base gameplay, there isn't a lot the player can do that actually matters.
The game is set up so that it's a shooter, but movement is basically not used. Movement of the player mostly consists of going to the right a little bit to adjust for getting knocked back. You can jump, but there's not a lot of reason to. When you do jump, it feels clumsy. You can't evade enemies too well anyway via movement, due to the small playfield. I think it also might be a hitbox thing: When I try to jump over the green dudes, they usually end up punching me when it looks like my legs are missing them completely.
Worse, the game is a shooter in which your aim really doesn't matter. Since enemies also basically just move to the front of you from the right of the screen, you don't need to change dong angles/aim (henceforth to be known as dA). The dA also doesn't need to be changed much because you have a perpetual spray, rather than a punctuated spurt or a quickly depleted spray. You can basically just hold the mouse button down, which further makes it feel like the player's input doesn't matter that much.
In short, the player doesn't really have to maneuver and he doesn't really have to aim.
Suggestions:
- Make Mann spurt (-.O ._-O :._O) rather than spray (-----------), for about the same damage over time. The powerups could temporarily give you back your continuous spray mode.
- Enemies that move to areas of the screen not directly in front of you, then charge up before attacking you. Requires the player to adjust their aim to shoot them down before they get shot.
- Make the jump hitbox smaller. Possibly give the jump some other function. I think a spinning teabag stomp attack would add a lot to the artistic subtext of the game.
Alternatively, ignore everything I just typed and add more bosses per stage and a randomized appearance to the girl sprite.