How to Make Bullets Follow the Mouse Cursor in PyGame?

Firing Bullets towards the Cursor in PyGame

In PyGame, creating projectiles that follow the mouse cursor's direction can pose a challenge. Let's examine the provided code and address its shortcomings.

Existing Code Analysis

The current code aims to:

• Create a Bullet class to represent projectiles.
• Initialize a Game class to handle bullet generation and movement.

However, the implementation has some flaws:

• It uses pygame.transform.rotate incorrectly, which returns a new rotated surface instead of transforming the original object.
• It attempts to calculate the movement direction and rotation angle dynamically, which leads to unpredictable bullet behavior.

Corrected Approach

To fix these issues, we adopt a different approach:

1. Initialize Bullet Parameters at Creation:

   • When creating a new bullet, calculate its starting position and direction vector towards the mouse cursor.
   • Normalize the direction vector to create a unit vector.

2. Pre-Rotate the Bullet:

   • Rotate the bullet surface to align with the calculated direction vector.

3. Continuous Position Updating:

   • Update the bullet's position by incrementally adding the scaled direction vector to its current position.

Example Implementation

<code class="python">import pygame
import math

# Bullet Class
class Bullet:
    def __init__(self, x, y):
        # Calculate initial position and direction
        self.pos = (x, y)
        mx, my = pygame.mouse.get_pos()
        self.dir = (mx - x, my - y)
        # Normalize direction vector
        length = math.hypot(*self.dir)
        self.dir = (self.dir[0]/length, self.dir[1]/length)
        
        # Create bullet surface and rotate it
        self.bullet = pygame.Surface((7, 2)).convert_alpha()
        self.bullet.fill((255, 255, 255))
        angle = math.degrees(math.atan2(-self.dir[1], self.dir[0]))
        self.bullet = pygame.transform.rotate(self.bullet, angle)
        self.speed = 2  # Adjust bullet speed as desired

    def update(self):
        # Update position based on scaled direction vector
        self.pos = (self.pos[0]+self.dir[0]*self.speed, self.pos[1]+self.dir[1]*self.speed)

    def draw(self, surface):
        # Draw bullet aligned with the correct direction
        bullet_rect = self.bullet.get_rect(center=self.pos)
        surface.blit(self.bullet, bullet_rect)

# PyGame Main Loop
pygame.init()
window = pygame.display.set_mode((500, 500))
clock = pygame.time.Clock()
bullets = []  # List to store bullet objects

while True:
    clock.tick(60)  # Set desired frame rate
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        elif event.type == pygame.MOUSEBUTTONDOWN:
            # Create a new bullet and add it to the list
            bullets.append(Bullet(*pygame.mouse.get_pos()))

    # Update and draw bullets
    for bullet in bullets[:]:
        bullet.update()
        if not window.get_rect().collidepoint(bullet.pos):
            # Remove bullets that leave the window boundary
            bullets.remove(bullet)
        else:
            # Draw bullet at its current position
            bullet.draw(window)

    # Render the updated display
    pygame.display.update()</code>

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