Ah, thanks. Maybe I'll give it a try with the keyboard. I did see keyboard commands at the beginning, then forgot about them when everything seemed mouse-controlled.
As to the menu/HUD problem, sounds like maybe I didn't quite explain it right - and retesting it right now to explain it better, it's not quite as straightforward as I thought, it only happens in some places. The best example I've got is level 4 (since that's where I am right now) - the upper right corner has a 2x2 "room" with multiple channels coming into it. If I click almost anywhere in the top-left square of that room, (or within a 4x2 rectangle up-left from that square), the options menu opens (as if I'd opened the HUD and clicked the options button).
I hope that makes sense - if not I'll try to record a video or take a screenshot later to show the area I mean.