Overall, great and polished entry! It's a classic with a small twist and the music fits well. My feedback is kinda already stated in other previous comments. I particularly agree with the need for a better conveying of who the enemy is. But my main issue is I played through the entire game without having to move the container.
Sure controlling the container helps strategize, block enemies, and collect coins, but since the ship can also move the cargo it just felt redundant. I wish there was a better need for moving the container with arrow keys, especially because this is where your take on the theme shows the most.