how to control snake with only two keys i.e left and right

问题

currently, i'm using all four keys to steer the snake left, right, up and down. I'm wondering how can i only use left and right key to move the snake around.

                    if event.key == pygame.K_LEFT:
                        snake.direction = 2
                    elif event.key == pygame.K_RIGHT:
                        snake.direction = 3
                    elif event.key == pygame.K_UP:
                        snake.direction = 0
                    elif event.key == pygame.K_DOWN:
                        snake.direction = 1
    def move(self):
        if self.direction is 0:
            self.dy = -self.block
            self.dx = 0
        if self.direction is 1:
            self.dy = self.block
            self.dx = 0
        if self.direction is 2:
            self.dy = 0
            self.dx = -self.block
        if self.direction is 3:
            self.dy = 0
            self.dx = self.block
        self.x += self.dx
        self.y += self.dy

can anyone guide me how to do that?

回答1:

Define the directions as follows:

• 0: move up
• 1: move right
• 2: move down
• 3: move right

def move(self):
    if self.direction is 0:
        self.dy = -self.block
        self.dx = 0
    if self.direction is 1:
        self.dy = 0
        self.dx = self.block
    if self.direction is 2:
        self.dy = 0
        self.dx = -self.block
    if self.direction is 3:
        self.dy = self.block
        self.dx = 0

    self.x += self.dx
    self.y += self.dy

When right is pressed then add 1 to snake.direction and when left is pressed the subtract 1. Use the % (modulo) operator (see Binary arithmetic operations) to ensure tha the result is in rage [0, 3]:

if event.key == pygame.K_LEFT:
    snake.direction = (snake.direction - 1) % 4
if event.key == pygame.K_RIGHT:
    snake.direction = (snake.direction + 1) % 4

回答2:

                if event.key == pygame.K_LEFT:
                    if snake.direction == 0
                        snake.direction = 2
                    elif snake.direction == 2
                        snake.direction = 1
                    elif snake.direction == 1
                        snake.direction = 3
                    elif snake.direction == 3
                        snake.direction = 0
                elif event.key == pygame.K_RIGHT:
                    if snake.direction == 0
                        snake.direction = 3
                    elif snake.direction == 3
                        snake.direction = 1
                    elif snake.direction == 1
                        snake.direction = 2
                    elif snake.direction == 2
                        snake.direction = 0
def move(self):
    if self.direction is 0:
        self.dy = -self.block
        self.dx = 0
    if self.direction is 1:
        self.dy = self.block
        self.dx = 0
    if self.direction is 2:
        self.dy = 0
        self.dx = -self.block
    if self.direction is 3:
        self.dy = 0
        self.dx = self.block
    self.x += self.dx
    self.y += self.dy

This should rotate your snake based on the direction it was traveling before.

回答3:

Rather than set the direction based on keypress, have the left and right keys adjust the direction by adding or subtracting from the current direction.

I've also changed the move function so that the directions are in clockwise order.

                if event.key == pygame.K_LEFT:
                    snake.direction -= 1
                elif event.key == pygame.K_RIGHT:
                    snake.direction += 1

                if snake.direction > 3:
                    snake.direction = 0
                elif snake.direction < 0:
                    snake.direction = 3
def move(self):
    if self.direction is 0:
        self.dy = -self.block
        self.dx = 0
    if self.direction is 1:
        self.dy = 0
        self.dx = -self.block
    if self.direction is 2:
        self.dy = self.block
        self.dx = 0
    if self.direction is 3:
        self.dy = 0
        self.dx = self.block
    self.x += self.dx
    self.y += self.dy

来源：https://stackoverflow.com/questions/61862293/how-to-control-snake-with-only-two-keys-i-e-left-and-right