Introduction to Game Development Lesson 0: Pong

Simple Pong by Peter Kwak (Edited by Topher Pedersen)

On my way back to Dallas from Austin on Labor Day I happened to hear about this really awesome course on game development from Harvard University taught by David Malan (of CS50) and Colton Ogden. I immediately enrolled in the course via on my phone, and jumped right into lesson 0 after I arrived back in Dallas.

One of the things that I really liked about the course is that they kick things off with one of the original video games, Pong. When I first started teaching at theCoderSchool this was one of the first games I built myself to make sure I knew what I was doing when it game to programming simple 2D games in Python with my students. That first summer of teaching we actually used an extremely slimmed down ~100 line version of the game one of my coworkers Peter Kwak wrote for our summer camp.

Fast forward a few hours though, and I’ve quickly fallen out of love with Malan & Ogden’s course. While the Lua programming language and Love2D game engine seem really promising, their code examples haven’t been updated in two years, and include bugs that prevent them from running. While I was able to find a bug fix that someone posted in the YouTube comments for the course lecture, I realized that the 100 line program that Peter wrote is actually a lot better for teaching purposes than the one used in the Harvard CS50 Game Development Course on edX. So…

I busted out Peter Kwak’s old code, and modified it a little bit so I can run it using real Python instead of the web based stuff we were using at camp. I imagine I will probably need to make a lot of tweaks to this code, however, I’m tossing two of my 10 year old students into the deep end of the pool tomorrow with Lesson 0: Pong =>

# Copyright (c) 2018 Peter Kwak (Edited by Chris Pedersen)
# This is free and unencumbered software released into the public domain.
# For more information, please refer to <>
import turtle
# Create Game Window
screen = turtle.Screen()
# screen.setup(500, 400)
screen.screensize(500, 500, "black")
# screen.addshape("Paddle.jpg")
# Create Ping Pong Ball
ball = turtle.Turtle()
# Create Left Ping Pong Paddle
paddle1 = turtle.Turtle()
paddle1.shapesize(4.5, 1, 0)
# Create Right Ping Pong Paddle
paddle2 = turtle.Turtle()
paddle2.shapesize(4.5, 1, 0)
# Create Scoreboard
scoreWriter = turtle.Turtle()
# Set Ball Trajectory
rise = 3
run = 3
# Set Score
score1 = 0
score2 = 0
# Create Function Which Will Move Player 1's Paddle Up
def up1():
paddle1.sety(paddle1.ycor() + 50)
# Create Function Which Will Move Player 1's Paddle Down
def down1():
paddle1.sety(paddle1.ycor() - 50)
# Create Function Which Will Move Player 2's Paddle Up
def up2():
paddle2.sety(paddle2.ycor() + 50)
# Create Function Which Will Move Player 2's Paddle Down
def down2():
paddle2.sety(paddle2.ycor() - 50)
# Create Function To Update Scoreboard
def updateScoreboard():
global scoreWriter
global score1
global score2
global ball
myFont = ("Arial", 40, "bold")
scoreWriter.goto(-100, 150)
scoreWriter.write(score1, font=myFont)
scoreWriter.goto(100, 150)
scoreWriter.write(score2, font=myFont)
ball.goto(0, 0)
# Set Event Listeners
# These event listeners will listen for button presses (up, down, etc.)
screen.onkey(up1, "w")
screen.onkey(down1, "s")
screen.onkey(up2, "Up")
screen.onkey(down2, "Down")
# Create Main Game Loop (Simulates Time, Keeps Game Running)
while True:
# Move Ball
ball.goto(ball.xcor() + run, ball.ycor() + rise)
# Detect Top or Bottom Boundary Strike
# (Reverses the Ball's Direction of Travel)
if ball.ycor() > 200 or ball.ycor() < -200:
rise = -rise
# Detect Paddle Strike (Player 1)
# (Also Reverses the Ball's Direction of Travel)
if abs(paddle1.xcor() - ball.xcor()) < 15:
if abs(paddle1.ycor() - ball.ycor()) < 50:
run = -run
# Detect Paddle Strike (Player 2)
# (Also Reverses the Ball's Direction of Travel)
if abs(paddle2.xcor() - ball.xcor()) < 15:
if abs(paddle2.ycor() - ball.ycor()) < 50:
run = -run
# Detect When A Player Scores a Point
if ball.xcor() > 250:
# Increment player1's score by 1 point when his ball
# travels past the paddle of his opponent, player 2.
score1 = score1 + 1
ball.goto(0, 0)
elif ball.xcor() < -250:
# Increment player2's score by 1 point when his ball
# travels past the paddle of his opponent, player 1.
score2 = score2 + 1
ball.goto(0, 0)
# Christine, My Super Sweet AI Goes HERE...
if ball.ycor() > paddle2.ycor() + 25:
paddle2.sety(paddle2.ycor() + 15)
elif ball.ycor() < paddle2.ycor() - 25:
paddle2.sety(paddle2.ycor() - 15)
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