Intermediate — Day 1

# INSTRUCTOR — Day 1: Libraries & Turtle Graphics (Intermediate)
# -----------------------------------------------
# TEACH: Students already know variables, types, and basic conditionals.
# Move quickly through the review. The real focus is the Turtle library.
# Key vocabulary: library, import, screen, turtle object, tracer, penup/pendown.

import turtle

# TEACH: import makes an external library available. Without it, turtle is undefined.
# Demo: try turtle.Screen() before the import line → NameError.

# --- Screen setup ---
screen = turtle.Screen()
screen.bgcolor("black")         # TEACH: color names are strings
screen.setup(width=600, height=600)
screen.tracer(0)                # TEACH: tracer(0) disables automatic drawing.
                                # We must call screen.update() manually.
                                # This is how we control animation speed later.

# --- Turtle object ---
t = turtle.Turtle()
t.shape("square")               # TEACH: shapes available: "square", "circle", "arrow", "turtle"
t.color("white")
t.penup()                       # TEACH: penup means moving doesn't draw a line
t.goto(0, 0)                    # TEACH: (0,0) is the CENTER of the screen

screen.update()                 # TEACH: without this, nothing appears on screen with tracer(0)

# TEACH: coordinate system — show the axes on a diagram
# x: negative = left,  positive = right
# y: negative = down,  positive = up
# Center (0,0), corners at approx ±300 on a 600×600 screen

screen.mainloop()               # TEACH: keeps the window open; without it the window closes instantly

# INSTRUCTOR — Day 1: Project: Snake: Screen & Head Setup (Intermediate)
# -----------------------------------------------
# TEACH: This is the foundation of every future session.
# Every student must leave Day 1 with this file working.
# Check: black window open, white square visible in the center.
# Common issue: window appears and immediately closes — they forgot screen.mainloop().

import turtle

# --- Screen ---
screen = turtle.Screen()
screen.title("Snake Game")      # TEACH: title() sets the window title bar text
screen.bgcolor("black")
screen.setup(width=600, height=600)
screen.tracer(0)

# --- Snake head ---
head = turtle.Turtle()
head.shape("square")            # TEACH: the snake body will also use squares
head.color("white")
head.penup()                    # TEACH: we NEVER want head to draw lines as it moves
head.goto(0, 0)

# TEACH: naming convention — we call it 'head' not 't' because it will have a specific role.
# Every future Day builds on these exact variable names. Don't rename them.

screen.update()
screen.mainloop()

# INSTRUCTOR — Day 1: Extra Activity: Draw a Pattern (Intermediate)
# -----------------------------------------------
# TEACH: for loops + Turtle = immediate visual feedback.
# Key insight: turn angle = 360 / number of sides.
# Students should try different values and see the pattern emerge.

import turtle

turtle.speed(5)
turtle.color("purple")

# Draw a hexagon (6 sides, 60 degrees each)
for i in range(6):
    turtle.forward(100)
    turtle.right(60)    # 360 / 6 = 60

turtle.done()

# TEACH: what shape do you get with range(3), right(120)? Triangle.
# range(4), right(90)? Square. range(8), right(45)? Octagon.

# TEACH: challenge — draw the shape 4 times by wrapping in another for loop
# Students must figure out how to move the turtle between drawings

# Challenge extension:
import turtle as t
t.speed(0)
positions = [(-150, 0), (150, 0), (0, 150), (0, -150)]
for pos in positions:
    t.penup()
    t.goto(pos)         # pos is a tuple (x, y) — goto accepts it directly
    t.pendown()
    for _ in range(6):
        t.forward(60)
        t.right(60)

t.done()