It's innovative, and funny. But I'm not sure this is fun. The bouncing tower placement seems to work against the idea of tower defense, making managing your resources utter chaos. This would be ok as a challenge if we could still plan for it, but the projectiles seem to wobble about and have a mind of their own instead of being reliable distance/bounce bullets. So even with what feels like the "right" angle and power from last play, the gun won't land in the same spots when the level is tried again.
I also had several bugs, like sometimes the currency would just float around the cursor instead of being collected. This basically killed me the first game I played as I can't spend the currency if it hasn't collected yet.
Last, you can cheese it really badly if you just always shoot very low speed defense spawns right around the player. I think having a ranged or exploding enemy would help eliminate this issue, so we have to keep the enemy far away. I surrounded the shooting point with the first guns and was basically immortal after that.
One idea you could try is to make the guns defense based on how much "oomph" the player shot them with, or perhaps even how many wall bounces the gun did before stopping. That would encourage taking the risky bouncy shots over the safe small putts.
I feel a game to be found here if you embrace the chaos and balance for it carefully. It started being a little fun every now and then.
I think with some clever level designs, and better physics for shooting the defenses, this could really become something great.