First program using Pymunk

import pymunk as pm
from pymunk.vec2d import Vec2d
import pygame
from pygame.locals import QUIT

# Initialize Pygame
pygame.init()
screen = pygame.display.set_mode((600, 600))
clock = pygame.time.Clock()

# Create a space
space = pm.Space()

# Create a center body
center_mass = 10
center_moment = pm.moment_for_poly(center_mass, [(-100, -100), (100, -100), (100, 100), (-100, 100)])
center_body = pm.Body(center_mass, center_moment)
center_body.position = Vec2d(300, 300)  # Center of the screen

# Create a vertex body
vertex_mass = 1
vertex_radius = 20  # Enlarged radius
vertex_moment = pm.moment_for_circle(vertex_mass, 0, vertex_radius)
vertex_body = pm.Body(vertex_mass, vertex_moment)
vertex_body.position = Vec2d(400, 400)  # Position at one of the vertices

# Create shapes
center_shape = pm.Poly(center_body, [(-100, -100), (100, -100), (100, 100), (-100, 100)])
vertex_shape = pm.Circle(vertex_body, vertex_radius)
vertex_shape.sensor = True

# Add bodies and shapes to the space
space.add(center_body, center_shape)
space.add(vertex_body, vertex_shape)

# Create a PinJoint
ancher1 = Vec2d(100, 100)  # Relative to center_body
ancher2 = Vec2d(0, 0)  # Relative to vertex_body
pj = pm.PinJoint(center_body, vertex_body, ancher1, ancher2)

# Add the PinJoint to the space
space.add(pj)

# Main loop
running = True
while running:
    for event in pygame.event.get():
        if event.type == QUIT:
            running = False

    # Clear screen
    screen.fill((255, 255, 255))

    # Step the simulation
    space.step(1/60.0)

    # Draw the center body
    center_pos = center_body.position
    pygame.draw.polygon(screen, (102, 178, 255), [(center_pos.x + x, center_pos.y + y) for x, y in [(-100, -100), (100, -100), (100, 100), (-100, 100)]])

    # Draw the vertex body
    vertex_pos = vertex_body.position
    pygame.draw.circle(screen, (0, 0, 0), (int(vertex_pos.x), int(vertex_pos.y)), vertex_radius)

    # Draw the PinJoint
    pygame.draw.line(screen, (255, 102, 102), (center_pos.x + ancher1.x, center_pos.y + ancher1.y), (vertex_pos.x + ancher2.x, vertex_pos.y + ancher2.y), 2)

    # Update the display
    pygame.display.flip()
    clock.tick(60)

pygame.quit()