iterate_code_versions

# Re-written version of fly_my_birds:
# - use functions to paint the seascape, to draw the bird, and to
#     update its position
# - use one tuple birdpos instead of two variables birdx and birdy
# Copyright 2023 Roland Richter

from __future__ import division, print_function

# Define the background colour; it should be constant, i.e. never be modified.
# https://peps.python.org/pep-0008/ states: "Constants are ... written in
# all capital letters with underscores separating words."
BG_COLOUR = "#87CEEB"   # Light sky blue

# setup() is called only once, at start-up
def setup():
    size(800, 500)
    background(BG_COLOUR)

    # The birds position: let it start at the upper right edge;
    # birdpos is a pair of coordinates (x,y); Python calls this a tuple.
    global birdpos
    birdpos = (width - 40, 0)
    frameRate(8)


# draw() is called repeatedly
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(BG_COLOUR)

    paint_seascape()

    global birdpos
    birdpos = update(birdpos)

    draw_bird(birdpos)


# The following functions are commented with a so-called docstring,
# see https://peps.python.org/pep-0257/

def paint_seascape():
    """Paint a green island, the sea, and the sun."""
    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)


def update(pos):
    """Return an updated position.

    Arguments:
    pos -- the current position as a (x,y) tuple
    """
    # The first item of a tuple has index 0, the second has index 1.
    return (pos[0] - 5, pos[1] + 2)


def draw_bird(pos):
    """Draw a bird at the given position.

    Arguments:
    pos -- the current position as a (x,y) tuple
    """
    # Unpack the x and y value of the position
    (birdx, birdy) = pos

    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)

# ----------------------------------------------------------------------
# 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/>.