I love this kind of game! Maybe I'll get to work on such a concept later. But it was sufficiently entertaining. The shader/vignette effects were very nice! Quite unfortunate that there was no sound, even a simple music track would've elevated this game a lot! The only other complaint I have is that there's no "back" button when I click on the combine section. It forces me to combine the plants. Maybe another thing would be that I would've appreciated a second "level" but I think i'm asking for too much at this point.
I can only say nicely done for a solo game! I hope my feedback was insightful!