The two guy problem

main.py

import pygame
import math

start_x = 50
start_y = 150
start_dist = 300
top_guy = [start_x,start_dist+start_y]
bottom_guy = [start_x,start_y]
vel = 0.1
angle = 0

resolution = [1000, 500]
pygame.init()
window = pygame.display.set_mode(resolution)

font = pygame.font.Font(pygame.font.get_default_font(),20)
dist = math.sqrt((bottom_guy[0]-top_guy[0])**2 + (bottom_guy[1] - top_guy[1])**2)
dist_text = font.render("distance="+str(dist), False, (255,255,255))
window.blit(dist_text, (10,10))
pygame.draw.circle(window, (0,0,255), top_guy, 3)
pygame.draw.circle(window, (255,0,0), bottom_guy, 3)
pygame.display.update()

while 1:
    pygame.draw.line(window, (0,0,0),bottom_guy, top_guy)
    top_guy_next = [top_guy[0]+vel, top_guy[1]]
    bottom_guy_next = [bottom_guy[0] + math.sin(angle)*vel, bottom_guy[1] + math.cos(angle)*vel]
    pygame.draw.line(window,(255,0,0),bottom_guy, bottom_guy_next)
    pygame.draw.line(window,(0,0,255), [start_x, start_y+start_dist], top_guy_next)
    bottom_guy = bottom_guy_next
    top_guy = top_guy_next
    pygame.draw.line(window, (255,255,255), bottom_guy, top_guy)
    angle = math.atan((top_guy[0]-bottom_guy[0])/(top_guy[1]-bottom_guy[1]))
    window.set_at((round(top_guy[0]),round(top_guy[1])), (0,0,255))
    window.set_at((round(bottom_guy[0]),round(bottom_guy[1])), (255,0,0))
    pygame.draw.rect(window, (0,0,0), (0,0,500,100))
    dist = math.sqrt((bottom_guy[0]-top_guy[0])**2 + (bottom_guy[1] - top_guy[1])**2)
    dist_text = font.render("distance="+str(dist), False, (255,255,255))
    window.blit(dist_text, (10,10))
    pygame.display.update()