Very cool concept! Unfortunately you set your priorities wrong when it came to the art department. You have such a clean and cool looking gold wagon and very cool attack animations, but lack player and enemy sprites (even tho I know you finished your player sprites). I also believe you should take another look at balancing the stages, as the player has 0 clue on what they are doing when they first spawn in, I personally think the first wave is way too tough.
I am huge fan of the different attack types and think you guys did a really good job showcasing them!