Really polished and fun game, great job! I like how taking away control from TD resulted in a kind of frantic action game. The difficulty felt reasonable, even if it eventually got to a point where most enemies got completely obliterated, as that's part of the TD experience I think. Great visuals and audio as well; very impressive for the time scale.
The one issue (that others have already said) is the placement mechanic did feel a bit hollow. With no choice, and no reason not to press E as soon as possible, it may as well have been automatic. If you plan to develop it further, maybe you could add some other use for the resource, like upgrading your ship's speed or fire rate. That way there would be a quick choice to make about how to spend it.