Good, but...
First I'm like to say this was a wonderfully designed, illustrated and coloured game, so place don't take this as a total flame, but I think some things need improving.
First, the 'enemies'. Hardly any of these really do any damage to plants, in fact, they mostly help them, so that's one thing that caught my attention. Secondly, they're very imbalanced compared to your weapons, which seem very expensive and take a long time to buold once you place them. Also, spacing seems very sparce, and could be given a tighter grid. Then there's the music, which eventually cuts out, and the 'Pause' doesn't really help you plan, seeming to try and hide what's going on from your veiw.
It seems that some extra thought needs to go into the game itself, as well as the inticate presentation. Keep it up, though, I'd like to see what else you produce.