incredibly annoying to "idle" when even looking at the comments below pause the game. The game has to be displayed on the monitor (not even minimazing on its on separate window will work) for the game to run.
"continue" should auto next level instead of needing to select from lobby. "retry" doesn't work when you die. Arrow Keys scrolls the whole page which is annoying. Would benefit from some chill BGM. Otherwise the simplicity of the game makes it a nice relaxing puzzle game.
Having trouble? Remember, it's quantity, not quality so much that matters.
What works for me, is I buy one, and then only upgrade its damage. And then buy more units. Until I've got my quantity, then I choose my quality.
Hope this helps. ;)