Movement

     A red ball on the screen is mighty exciting, isn't it? Well, it's about to get better. But just a little. We're going to move the ball. We're going to add 3 new lines between the exit block and the line before:

import pygame, sys
pygame.init()
screen=pygame.display.set_mode([640, 480])
screen.fill([255, 255, 255])
ball = pygame.image.load("Ball.png")
screen.blit(ball, [50, 50])
pygame.display.flip()
pygame.time.delay(2000)
screen.blit(ball, [200, 50])
pygame.display.flip()
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT: sys.exit()

     Whoa. 2,000 seconds. But, just run the program. All of a sudden...

     I don't necessarily think that counts as moving. Remember, blitting is copying. So, in video games, nothing actually moves. A new version of an image is created for every movement it makes, pixel by pixel. This means we have to wipe the original image from existence. Actually, truth be told, that can't exactly be done. We have to paint over the original. We have to erase the original image before we flip the screen and show the new one. There's only one line of code that needs to be added, right before the flip() function. And just so you know, the picture is 150 by 150 pixels.

import pygame, sys

pygame.init()

screen=pygame.display.set_mode([640, 480])

screen.fill([255, 255, 255])

ball = pygame.image.load("Ball.png")

screen.blit(ball, [50, 50])

pygame.display.flip()

pygame.time.delay(2000)

screen.blit(ball, [200, 50])

pygame.draw.rect(screen, [255, 255, 255], [50, 50, 150, 150], 0)

pygame.display.flip()

while True:

    for event in pygame.event.get():

        if event.type == pygame.QUIT: sys.exit()

     Now when you run it, the problem should be solved.

     Much better!
     So, that's our ball that moves simply once. Let's see if we can get the animation smoother! Let's change the program so it makes smaller steps, and make it keep moving.

import pygame, sys
pygame.init()
screen=pygame.display.set_mode([640, 480])
screen.fill([255, 255, 255])
ball = pygame.image.load("Ball.png")
x=50
y=50
screen.blit(ball, [x, y])
pygame.display.flip()
while True:
    pygame.time.delay(20)
    pygame.draw.rect(screen, [255, 255, 255], [x, y, 150, 150], 0)
    x=x+5
    screen.blit(ball, [x, y])
    pygame.display.flip()
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

     You see, it spawns the ball at the points of x and y, and while the program is True (still running), it will move the ball directly to the right every 20 milliseconds, erasing the original with a block of white. In order to avoid erasing the current one, the previous one has to be painted over first. Remember that for fluid movement!
     When you run the program, the ball will move smoothly, but then it goes off of the screen, since it doesn't have any functions to bounce off of the side of the screen or anything. But the good thing is that it doesn't strobe white as it could have done!
     Wow, this article is getting really long. Think of it as an apology for the rate of my article writing this year. Anyway, see you next time!