Implementing Automatic Missile Tracking in Python with Pygame

Automatic missile tracking is a common technique in shooting games, which can be derived from solving differential equations and using simple trigonometry.

The algorithm divides time into small intervals, constructs a triangle each interval to compute the direction (angle a) and distance (vt) the missile should travel, updates the missile position, and repeats.

Key formulas: distance between missile and target, sin(a) = (y1‑y)/distance, cos(a) = (x‑x1)/distance, and the new position is x1+vt*cos(a), y1‑vt*sin(a).

Implementation in Python with pygame:

<code>import pygame,sys
from math import *
pygame.init()
screen=pygame.display.set_mode((800,700),0,32)
missile=pygame.image.load('element/red_pointer.png').convert_alpha()
x1,y1=100,600  # missile start
velocity=800
time=1/1000
clock=pygame.time.Clock()
old_angle=0
while True:
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
            sys.exit()
    clock.tick(300)
    x,y=pygame.mouse.get_pos()
    distance=sqrt(pow(x1-x,2)+pow(y1-y,2))
    section=velocity*time
    sina=(y1-y)/distance
    cosa=(x-x1)/distance
    angle=atan2(y-y1,x-x1)
    x1,y1=(x1+section*cosa,y1-section*sina)
    d_angle = degrees(angle)-old_angle
    old_angle = degrees(angle)
    missiled = pygame.transform.rotate(missile, -degrees(angle))
    screen.blit(missiled, (x1-missile.get_width(), y1-missile.get_height()/2))
    pygame.display.update()</code>

To keep the missile tip aligned after rotation, the code computes the rotated image’s head position and adjusts the blit coordinates accordingly, handling four angle quadrants.

Full source code with quadrant handling is provided, enabling a smooth missile‑tracking demo.