Like Baghernia I got the "installer integrity check" msg after several attempts. I noticed that the size of the download file, in Windows Explorer, was less than my browser (Firefox) said it was, though the actual size was different with each download. But eventually I got a download that worked. Clearly there's something wrong with the downloading process.
There are no less than 4 tips about having symbiosis between two plants, including how to discontinue it, but nothing about setting it up. I've managed to do several levels at more than the basic level of difficulty without using symbiosis, but, given the name of the game, it must be necessary to use it.
I cannot figure out how to play this game at all. All I can do is view the castle and fire 5 shots, but no way even to alter how I fire the shots so none of them go anywhere near the castle.
I don't like point and click adventure games in general, but I liked this one. Partly it is its simplicity as a game, so that you can forget about it being a game, about any need to act or interact as a player, and regard it rather as a short story which you are reading. It is a story about a story, so it reminds me more of one of Jorge Luis Borges's short stories than one of Jacques Derrida's attempts at deconstruction. There is no attempt within the story to deconstruct the story to be traded. In fact the story within the story is simply taken to be true, i.e. it is non-fictional, it is about the same world. In fact I did not find the story within the story memorable or particularly interesting in itself, but only as an element in the story in which it is to be traded.
 "Defender's Quest (lengthy!) Demo"){kind=icon}
 "Symbiosis"){kind=icon}
 "Crush the Castle"){kind=icon}
 "The Trader of Stories"){kind=icon}