fireworks_sprites.py

# fireworks_sprites.py - show a bunch of fireworks
# the "fireworks_spritesheet.bmp' file can be found in the "bmps" directory
# more info and video demo at this gist:
#  https://gist.github.com/todbot/f5a013918c208451424cea9d701f99c5
# 4 Jul 2022 - @todbot / Tod Kurt
import time, random
import board
import displayio
import rainbowio
import adafruit_imageload

fireworks_count = 5
sprite_fname = "fireworks_spritesheet.bmp"
sprite_count = 30*1
sprite_w,sprite_h = 64,64

display = board.DISPLAY  # our board has built-in display
dw,dh = display.width, display.height  # convenience values

sprite_sheet, sprite_palette = adafruit_imageload.load(sprite_fname)

maingroup = displayio.Group()  # all fireworks go on 'maingroup'
display.root_group = maingroup

def random_xy():
    return random.randint(0, dw-sprite_w), random.randint(dh//2, dh//2+20)

def copy_palette(p):  # this is fastest way to copy a palette it seems
    new_p = displayio.Palette(len(p))
    for i in range(len(p)):  new_p[i] = p[i]
    return new_p

def new_colors(p):  # first two colors after bg seem to be the "tails"
    p[1] = rainbowio.colorwheel( random.randint(0,255) )
    p[2] = rainbowio.colorwheel( random.randint(0,255) )


# holds list of sprites,sprite_index,x,y,launch_time
fireworks = [(None,0,0,0, 0) ] * fireworks_count
# make our fireworks
for i in range(len(fireworks)):
    pal = copy_palette(sprite_palette)
    pal.make_transparent(0)  # make background color transparent
    x,y = random_xy()
    start_index = random.randint(0,sprite_count-1)  # pick random point in fireworks life to start
    fwsprite = displayio.TileGrid(sprite_sheet, pixel_shader=pal,
                            width = 1, height = 1,
                            tile_width = sprite_w, tile_height = sprite_h)
    fireworks[i]= (fwsprite, start_index, x, y, pal)  # add sprite, and initial index, x,y, palette
    maingroup.append(fwsprite)

while True:
    for i in range(len(fireworks)):
        (sprite, sprite_index, x,y, palette) = fireworks[i]  # get firework state
        # update firework state
        launching = sprite_index == 0 and random.random() < 0.9
        if launching:
            y = y - 3  # move towards top of screen
        else:
            sprite_index = sprite_index + 1  # explode!
        # firework finished
        if sprite_index == sprite_count:
            sprite_index = 0   # firework is reborn, make a new x,y for it
            x,y = random_xy()  #random.randint(dw//4, 3*dw//4), random.randint(dh//2,dh//2+20)
            new_colors(palette)
        # update firework on screen
        sprite[0] = sprite_index  # set next sprite in animation
        sprite.x, sprite.y = x,y  # set its x,y
        # save the firework state
        fireworks[i] = (sprite, sprite_index, x,y, palette)
    time.sleep(0.008)  # determines our framerate