The game is overall good, the balancing and structure is essentially Plant vs Zombies, but that game also have good structure in general so it also propagates here as well. The main carrier would be the art with animation specifically, considering jam type it helps a lot. There's also details such as higher energy version of the music playing when there are more enemies (though the fade in should be a bit slower).
As for the compression issue, you might want to check type of interpolation/aliasing and make it something like average pixel or bilinear, it seems to be using Nearest neighbor. Some sprite such as bullet could also be on the top Z layer instead. Itch Io has an option to make the game open to new screen on HTML version below the upload, might want to look it up.