Development and castling: a new piece every move, king safe by move 10

Put pawns and pieces where they hit the four central squares. Open with a d- or e-pawn, or a piece that hits the centre (Nf3, g3 and Bg2).

While pieces are still at home, every move should bring one out. In the opening, play only moves that develop a piece, open a line for one, or castle.

Each opening move should bring a NEW piece into the game. Only move a developed piece again if it captures, escapes, or gains a tempo.

Don’t move the king or a home rook while you still mean to castle. If you want to castle, leave the king and both rooks alone until you do.

An early queen gets chased, and every check she runs from develops a piece for them. Bring the knights and bishops out first; the queen comes after castling.

Get the king out of the centre by move 10. Castle as soon as the pieces between king and rook are out — before you start anything else.

The board defines the opportunity — a position where the principle applies — and Stockfish is the referee: a miss is counted only when the engine’s own line at that move embodies the principle, so the row never blames you for a rule the position did not ask for. The row reads as tests passed out of tests taken.