fly_my_bird

# Draws movements of a flying bird, reminiscent of paintings
# by Erika G. Klien (1900--1957), who was one of the leading
# proponents of Viennese Kineticism:
# https://sammlung.belvedere.at/people/1059/erika-giovanna-klien
# Copyright 2023 Roland Richter

from __future__ import division, print_function

# setup() is called only once, at start-up
def setup():
    size(800, 500)
    background("#87CEEB")   # Light sky blue

    # The birds position: let it start at the upper right edge;
    # birdx and birdy are global variables, since they are used
    # in this function, setup(), and in another function, draw().
    global birdx, birdy
    birdx = width - 40
    birdy = 0

    frameRate(8)


# draw() is called about 60 times/sec by default; but ...
# QUIZ Why is the frame rate only about 8 frames per second?
def draw():
    # If (and only if) the left mouse button is pressed, the
    # canvas is erased each time, resulting in a "flip book" effect.
    if mousePressed:
        background("#87CEEB")   # Light sky blue

    # TRY to reverse the logic above: if the left mouse button is pressed,
    #     the sketch should *not* re-paint the background, and vice versa

    # Paint the seascape: a green island, and the sea
    stroke("#483C32")  # "Dark lava"
    fill("#087830")    # "La Salle Green"
    circle(0.5*width, height, 0.6*height)

    noStroke()
    fill("#08457E") # "Dark cerulean"
    rect(0, 0.8*height, width, height)

    # Draw the sun
    fill("#FFFF00")  # Yellow
    circle(0.1*width, 0.2*height, 90)

    # Compute the new position of the bird, ...
    global birdx, birdy
    birdx -= 5   # short for "subtract 5 from birdx"
    birdy += 2   # short for "add 2 to birdy"

    # TRY to let the bird fly from the upper left to the lower right!

    # ... then draw the bird at its current position
    stroke("#000000")   # Black
    fill("#F3E5AB")     # Medium champagne

    # Test whether frameCount is even or odd, then draw the corresponding
    # bird. In this way, the sketch constantly switches back and forth
    # between the two variants.
    if frameCount % 2 == 0:
        triangle(birdx, birdy, birdx-70, birdy-18, birdx-55, birdy-5)
        triangle(birdx, birdy, birdx+70, birdy-18, birdx+55, birdy-5)
    else:
        triangle(birdx, birdy, birdx-70, birdy-5, birdx-55, birdy+8)
        triangle(birdx, birdy, birdx+70, birdy-5, birdx+55, birdy+8)

    # TRY adding more birds, or other moving objects

    # TRY adding a lighthouse with a light that flashes like
    #     on-off-off-off, on-off-off-off, ...


# ----------------------------------------------------------------------
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.