Cons:
I would add a background filter to match the color of the blocks.
I use Linux, I don't know if it's a global shortcut, but pressing W + CTRL in the current tab closes it, making the game quite difficult. I also didn't like restarting everything; I could simply go back to the beginning without having to collect coins again.
Some enemies are unrecognizable (but I think this is more due to the graphics). I jumped on a creature and didn't even notice because it blends into the background.
Pros:
The design is well done, and I didn't encounter any notable bugs (apart from the gunshot, whose design isn't visible).
The scenery and collisions were well utilized; I found it quite fun overall. I think it could be further expanded with space mechanics, like slower gravity and the like (because of the space/alien theme).
It has a lot of different elements, and I liked the variety. Honestly, it has a lot of potential, but it needs to make the most of the space style