26 Opening / Golden rules: A 1) Bf1-c4: The bishop controls the centre and has some control over the opponents side of the board.
Bf1-d3: The bishop blocks the d2 pawn, which blocks the bishop on c1.
Nb1-a3: On a3 the knight has less mobility and no control of the centre.
2) Bf1-c4 The bishop controls the centre and has some influence over the opponents side of the board. Bf1-b5+ Giving check is not correct in this position. Black can play 1. ...c7-c6 and the bishop must move again. Bf1-e2 Too modest. The move of the bishop makes castling possible but the bishop does not control the centre.
3) Nb8-c6 The best way to protect the pawn on e5. f7-f6 The pawn on f6 is in the way of the knight on g8. Moving this pawn can expose the uncastled Black king to an attack. It is too early to explain the consequences of 2. Nf3xe5. Qd8-e7 The queen protects the pawn on e5 but prevents the bishop on f8 from coming out.
4) Nb8-c6 A developing move attacking the queen. White must lose time now because the queen has to move again. c7-c5 The pawn attacks the queen, but on c5 the pawn is a bit in the way of the bishop on f8. d7-d6 Not a bad move, but not the best. White plays 2. Ng1-f3 and on 2. ... Nb8-c6 White can play 3. Bf1-b5 and keep the queen on d4.
5) Ng1-f3 The best square for the knight. White can castle next move. Qd1-f3 Only if Black is not careful, is this a good move, but after 1. ... Ng8-f6 Black has parried the mating threat. The queen on f3 is in the way of the knight on g1. Qd1-h5 Black plays 1. ... Qd8-e7 and on the next move chases away the queen with 2. ... Ng8-f6 costing White time.
6) 0-0 Black protects f7 with a developing move. Qd8-e7 The queen does not really protect f7. She is too valuable. Rh8-f8 Not a proper protecting move. Black cannot castle kingside anylonger.
7) 0-0 The king is safe. Excellent move. Bg5-e3 The bishop is well placed on g5. There is no reason to move the same piece twice in the opening unless it is under attack. Bg5xf6 An unnecessary exchange. Do not exchange if not necessary.
8) Ng8-f6 The right move. Here the knight controls two centre squares. Ng8-e7 The knight on e7 has less mobility than on f6. From there it controls two squares in the centre. Bc8-d7 A developing move, but the bishop is not so active on d7.
9) 0-0 White correctly applies the third golden rule – king safety. Nf3xe5 The pawn on e5 cannot be taken so easily. Black wins the knight by the double attack: 1. ... Qd8-a5+. Nf3-g5 A premature attack on f7. Black plays 1. ... d7-d5.
10) Ng1-f3 The move of the knight enables castling. On f3 the knight attacks e5 and he controls two centre squares. Bf1-b5 This is a good move when there is a knight on c6. The bishop can be chased away by a pawn. d2-d3 Not a bad move but the bishop on f1 cannot be developed to an active square anymore.
11) e2-e3 White must parry the threat Qh4xf2#. This is the only way. d2-d4 Defends against the mate on f2, but after 1. ... Bc5xd4 White just loses a pawn and there is the same mating threat. Ng1-f3 Sometimes developing is not right. Black gives mate on f2.
12) Qd1-d5 Now and then a quick attack on f7 is correct. Black can protect f7 only by 1. ... Ng8-h6, but with ‘capturing + material’ (2. Bc1xh6). White wins material. Nb1-c3 Good move but not the best. There are always exceptions to the rules. 0-0 Good move but not the best.