Played cold: title, then Tier I board 1. Three answers.
1) Where I lost the thread: what the NUMBER means. The bottom line tells me the clicks, so I never didn't know what to do; but sweeper instinct reads a number as "mines touching this square", and yours is "mines this piece could move to". I only got it from the How-to-play diagram (the two hand-laid panels). A player who starts in Tier I and never opens it reads a 0 the wrong way for a whole board. Also, your page says the campaign teaches the pieces one at a time, but board 1 already stands four kinds (knight, king, bishop, queen) on the glass.
2) Did any board make me guess? I didn't take your word: I ran your own solver over 920 boards read from boards/ (campaign + tiers, every 4th file). 920/920 certified: static boards uniquely determined, move-mode boards solved by provably-safe probes inside their budgets. Zero failures. So no.
3) Right-click on a piece, cold: I guessed "deselect" or "nothing". Right-click = flag is fine, that is the sweeper habit. Right-click-on-a-piece = pin its sight is the one verb that changes how you reason, holding two counts at once, and it is the only one with no affordance on the board. It lives on line 4 of the rules sheet.
The real win: hover sight. I learned "count = the squares it could move to" with the mouse, not by reading, and watching the bishop's 2 drop to 1 the moment I parked the queen in its line taught me the game in one move.