'''
''' playfield tutorial - part 1
'''
''' by greg smith
'''

'''
''' use c coordinates
'''
OPTION C_COORDS

dim x as int  'position of car from 0-480
dim y as int  'position of car from 0-300
dim z as int  'which image of car

dim sprite_field as int 'the sprite number of the playfield sprites
dim sprite_car as int   'the sprite number of the car sprites
dim car_left as int     'index into car sprite for going left
dim car_right as int    'index into car sprite for going right
dim car_up as int       'index into car sprite for going up
dim car_down as int     'index into car sprite for going down

'''
''' initialization
'''
sub init
    sprite_field = 0  'playfield sprite
    sprite_car = 1    'car sprite

    car_left=0        'car left image
    car_right=1       'car right image
    car_up=2          'car up image
    car_down=3        'car down image

    '''
    ''' the playfield sprite has 9 bitmaps
    ''' one for each of the different areas of the
    ''' playfield
    sprite sprite_field, "playfield.pic"

    '''
    ''' the car has 4 bitmaps one for each direction
    sprite sprite_car, "car.pic"

    '''
    ''' the car can be anywhere on the playfield from
    ''' x = 0-480
    ''' y = 0-300
    x=240  'center of the playfield
    y=150  'center of the playfield
    z=car_right
end sub

sub repaint
    dim field_x as int   '0,1,2 for the horizontal bitmap
    dim field_y as int   '0,1,2 for the vertical bitmap
    dim field as int     '0-8 for the bitmap currently visible
    dim car_x as int     '0-159 for the x coord on the screen
    dim car_y as int     '0-99  for the y coord on the screen

    field_x = x / 160    ' compute the horizontal bitmap
    field_y = y / 100    ' compute the vertical bitmap
    field = field_y*3 + field_x ' combine them to compute the bitmap number

    car_x = x mod 160  ' compute the car's position on the screen
    car_y = y mod 100  ' compute the car's position on the screen

    move sprite_field, 0, 0, field  'display the current field
    move sprite_car, car_x, car_y, z 'display the car 

    paper dkgrey  'transparent color for the car
    redraw        'redraw all the sprites
    
end sub

'''
''' process the keyboard
'''
sub get_keys
    if key(#KEY_UP) then   'move the car up
        y=y-3
        z=car_up
    end if
    if key(#KEY_DOWN) then 'move the car down
        y=y+3
        z=car_down
    end if
    if key(#KEY_LEFT) then 'move the car left
        x=x-3
        z=car_left
    end if
    if key(#KEY_RIGHT) then 'move the car right
        x=x+3
        z=car_right
    end if
end sub

'''
''' main subroutine
'''
sub mainsub
    init

    while true
        repaint
        get_keys
    wend
end sub

'''
''' call the main subroutine
'''
mainsub