The game is simple and the sound effects are satisfying. I know the grey bar is a sword, but it looks like a place holder. The game does ramp up overtime, but the game isn't that challenging. The player cannot take damage, and there is no reason to not camp by the ship, taking down the enemies with ease. Also, the song doesn't loop.
Overall, I like the simple approach to a tower defense game. Maybe instead of a sword, the player can have a gun, same with his clones. And touching the enemies makes the player loose bits. Also, try adding some incentives to make the player move away from the ship, making them balance risk and reward. A timer or score system would also improve the game so players can try to beat their high score.