I loved it! The game had some pretty surprising strategy too. I liked that the plant had less health than you did, so I'd often rush in to eat up the damage destined for the plant. The game wasn't too challenging, and the only reason I died was the aforementioned pickup glitch, which ended more runs than I'd like. I played around with it, and it looks like when you drop an item, it's randomly offsetted, and when the offset is too large, it can't be picked back up. May not be completely accurate, but that was my assessment, hope it helps.
You said you wanted to make a postjam version, and I want a postjam version too, so here's an idea. What if the puddle eventually dried out, and rain created a new puddle elsewhere? Might pose an issue when hordes of zombies are incoming and there's no damn water.
I loved the zombie dudes, they made such funny sounds, and looked so cute. Very nice game, but a tad unplayable due to the pickup glitch. With that gone, this game would be godly.