Mixing tower defence and action is a great idea! I liked having two things to do and a clear objective to defend. I liked the fonts and effects.
I think one or two help prompts at the start like saying how to get more fuel from the dummy would be good. I also ran out of fuel a lot, especially at the start, which was a little tricky when learning stuff.
I liked this a lot. If you expanded the mechanics a little and rebalanced this, you could turn it into a bigger game.