I was confused as hell for like 10 solid minutes before I started figuring stuff out. Clicking stuff is kind of hard for me, sometimes it takes a double click, and sometimes it doesn't, so I end up randomly placing too many tiles in some spots. I like the art you do have and the music though, and I think the mechanics are interesting as a starting point. As phil pointed out, specifically having to close each shape seems kind of unnecessary; I'd like to make large planes or weird stuff that doesn't have to close.
Otherwise, great work! I enjoyed playing it!