Thanks guys

About difficulty: The target audience is Swedish school kids at varying ages. It's not meant to be challenging for an experienced ag-player, nor for native English speakers.
About length: The observation sessions won't last more than 45 minutes (during which the test subjects will be video-taped), so there's no point in making it much longer. Even though playing the game straight through prolly won't take more than minutes for veterans like you, having to look up words in a dictionary will add to that time.
About generic responses: The entire game (backgrounds, animations and scripts) was put together within roughly 3 weeks, so everything is extremely rushed. I also wanted to have lots of hotspots to increase the vocabulary feedback. Of course, having lots of named hotspots without being able to interact with them is annoying. I still tried to vary the responses, but apparently not well enough

Markbilly, yes, some puzzles lack 'repeat'-functions; on the other hand you should be able to type 'exit' and start over the conversation. If I get the time, I'll improve that aspect.