Thanks very much for your feedback, everyone!
@ncase: Completely hear you on the controls. It *was* left-click to cast and right-click to reel, but right-click in the web player makes the contextual menu pop up (even if I disable it in the player settings when I build in Unity). I played with using the scroll wheel as alternative but ran out of time before I could get it to feel right, so went with the keyboard as a scrappy solution.