Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation

In chess, Nf3 is a common move for white at the beginning of a game. This move puts pressure on black's pawn on e5 and sets up a future attack on the center. Additionally, it allows for the development of the knight and paves the way for a castle. Nf3 also prepares for potential pawn moves in the future to gain more control of the board.

After White plays Nf3 in the opening, Black's move of c5 aims to challenge white's control over the center of the board. By placing pressure on white's d4 pawn, Black creates options for themselves while threatening capture. Playing c5 also allows Black to develop their pieces for better mobility and control. It is a strong response to Nf3 that sets the pace of the game.

White's move of c4 after Black plays c5 is a good response because it helps to gain control over the center, particularly the d5 square. This move also creates more space for the development of White's pieces and can help to put pressure on Black's pawns. In addition, c4 could lead to the creation of some pawn chains which can be quite advantageous in the endgame. By playing c4, White aims to establish a strong pawn structure and gain more control over the board in the early stages of the game.

In the Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation, after White plays c4, Black's move of g6 is a good response as it prepares for the development of Black's bishop to g7. Playing g6 also allows the king to move to safety on g7 and prepares for a future castle. Additionally, by playing g6, Black gains a foothold in the center of the board and prevents White from moving a pawn to g5 in the next few moves. This move can also be useful in creating a strong defense against possible attacks from White's pieces.

White's move of d4 after Black plays g6 is a good response as it helps White to gain control over the center of the board which sets up a future attack. This move also prepares for the development of the knight and opens up space for the bishop on c1. Additionally, d4 can be used to gain more control over the board in the early stages of the game and can be a part of White's strategy in future moves. By playing d4, White puts pressure on Black's position and prepares to gain control over the board in the upcoming moves.

After White plays d4 in the opening, Black's response of Bg7 is a solid move as it places the bishop on a strong diagonal and prepares for future castling. By playing Bg7, Black can also create the opportunity to execute a pawn swap with White's c4 pawn if necessary. Additionally, Bg7 can help to control the h8-a1 diagonal, preventing potential attacks from White's pieces. This move also allows Black to maintain a strong defense against any potential attacks from the opponent, while preparing to advance their pieces in the upcoming moves.

In the Modern Defense: Semi-Averbakh Variation, Pterodactyl Variation, after Black plays Bg7, White's move of e4 is a strong response as it helps to gain control over the center of the board. This move also enables White to open up the position of the bishop on f1, and clears a path for the queen to move in the future. Additionally, e4 could lead to the creation of some strong pawn structures that can be quite advantageous in the endgame. By playing e4, White also puts pressure on Black's position, stopping any potential activity on the black side of the board. This move sets up for White's strategy to gain control of the board and potentially execute a future attack.

After White plays e4 in the opening, Black's move of Qa5+ is a strong response as it forces White to move their king. This move also threatens the knight on f3 and creates a strong pressure on the central squares. Additionally, Qa5+ torments White's plans to castle, and can also be an attempt to create some space and potentially to execute a pawn swap. By playing Qa5+, Black sets up a strong position and aims to create some disruption in White's position, potentially gaining some advantage in the upcoming moves.