Keyboard Movement
=================

.. contents::
    :local:

Goals
-----

- Detect keyboard events
- The bad way to do keyboard movement
- The good way to do keyboard movement
- Moving with inertia and friction

Starter code
------------
:doc:`Pygame Template <pygame-template>`

Video Tutorial
--------------

.. raw:: html

    <iframe width="560" height="315" src="https://www.youtube.com/embed/YTi3eReExs4" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

What you should do
------------------

- See if you can make the ball move faster if the user is holding the ``B`` key.
    
    - In the event loop, under ``KEYDOWN``, print the event to check what value the ``B`` key is. 
    - Where the other key press code is, create an if-statement that checks if that key is pressed and modify either the speed or the acceleration.

Final code (basic movement)
---------------------------

.. code-block:: python

    # Basic Movement
    import pygame
    from pygame.locals import K_ESCAPE, KEYDOWN, QUIT

    pygame.init()

    WIDTH = 640
    HEIGHT = 480
    SIZE = (WIDTH, HEIGHT)

    screen = pygame.display.set_mode(SIZE)
    clock = pygame.time.Clock()

    # ---------------------------
    # Initialize global variables

    circle_x = 200
    circle_y = 200

    # ---------------------------

    running = True
    while running:
        # EVENT HANDLING
        for event in pygame.event.get():
            if event.type == KEYDOWN:
                if event.key == K_ESCAPE:
                    running = False
            elif event.type == QUIT:
                running = False
        
        # GAME STATE UPDATES
        # All game math and comparisons happen here
        keys = pygame.key.get_pressed()
        if keys[119] == True:  # w
            circle_y -= 10

        if keys[97] == True:  # a
            circle_x -= 10
        
        if keys[115] == True:  # s
            circle_y += 10
        
        if keys[100] == True:  # d
            circle_x += 10


        # DRAWING
        screen.fill((255, 255, 255))  # always the first drawing command

        pygame.draw.circle(screen, (0, 0, 255), (circle_x, circle_y), 30)

        # Must be the last two lines
        # of the game loop
        pygame.display.flip()
        clock.tick(30)
        #---------------------------


    pygame.quit()


Final code (acceleration and friction)
--------------------------------------

.. code-block:: python

    # Moving with acceleration and friction
    import pygame
    from pygame.locals import K_ESCAPE, KEYDOWN, QUIT

    pygame.init()

    WIDTH = 640
    HEIGHT = 480
    SIZE = (WIDTH, HEIGHT)

    screen = pygame.display.set_mode(SIZE)
    clock = pygame.time.Clock()

    # ---------------------------
    # Initialize global variables

    FRICTION = 0.1

    circle_x = 200
    circle_y = 200
    speed_x = 0
    speed_y = 0

    # ---------------------------

    running = True
    while running:
        # EVENT HANDLING
        for event in pygame.event.get():
            if event.type == KEYDOWN:
                print(event)
                if event.key == K_ESCAPE:
                    running = False
            elif event.type == QUIT:
                running = False
        
        # GAME STATE UPDATES
        # All game math and comparisons happen here
        keys = pygame.key.get_pressed()
        acceleration = 1

        if keys[119] == True:  # w
            speed_y -= acceleration

        if keys[97] == True:  # a
            speed_x -= acceleration
        
        if keys[115] == True:  # s
            speed_y += acceleration
        
        if keys[100] == True:  # d
            speed_x += acceleration
        
        speed_x *= 1 - FRICTION
        speed_y *= 1 - FRICTION

        circle_x += speed_x
        circle_y += speed_y


        # DRAWING
        screen.fill((255, 255, 255))  # always the first drawing command

        pygame.draw.circle(screen, (0, 0, 255), (circle_x, circle_y), 30)

        # Must be the last two lines
        # of the game loop
        pygame.display.flip()
        clock.tick(30)
        #---------------------------


    pygame.quit()