my general opinion is using the mouse for things like direction or camera movement is fine because it isn't a "button", but using the mouse buttons (LMB or RMB) is kinda a cop-out because they can be used to press multiple other buttons on screen. It take away from the challenge/restriction of the theme.
The mouse wheel is an unique control where yes it's a button, but still associated with the mouse as a whole, so it could still be used in the same way as LMB or RMB. You don't use it in that way, so I can see how it fits the theme. It's just my personal opinion & interpretation of the theme so people are welcome to disagree!
