Nice twist on the theme. Good job on the release!
Not sure if you want this feedback, but what I would try to do is:
* Ramp up the speed a bit more
* Make the player more distinct
* Add ways to fight back
* Maybe have the plants be a gray/transparent color. To exacerbate the
feeling of progress even more.
* Maybe start the game zoomed in on the player, and have the camera grow over time?
Would fit the theme as well.