Made the Snake Game!

Added Snake Game demo.

Day 21/README.md

@@ -0,0 +1,15 @@
+# Day 21 - Build the Snake Game Part 2: Inheritance & List Slicing
+
+- Built a snake game.
+- Learned about class inheritance and list slicing.
+
+```python
+# The Fish class inherits the attributes and methods of the Animal class
+class Fish(Animal):
+    def __init__(self):
+        super().__init__()
+```
+
+## Snake Game
+
+![Day_21_Snake_Game](https://user-images.githubusercontent.com/30333942/129274809-8c292e1e-28e4-4df5-a1b0-57b77155782a.gif)

Day 21/food.py

@@ -0,0 +1,18 @@
+from turtle import Turtle
+import random
+
+
+class Food(Turtle):
+    def __init__(self):
+        super().__init__()
+        self.shape("circle")
+        self.penup()
+        self.shapesize(stretch_len=0.5, stretch_wid=0.5)
+        self.color("red")
+        self.speed("fastest")
+        self.refresh()
+
+    def refresh(self):
+        random_x = random.randint(-280, 280)
+        random_y = random.randint(-280, 255)
+        self.goto(random_x, random_y)

Day 21/main.py

@@ -0,0 +1,51 @@
+from turtle import Screen
+from snake import Snake
+from food import Food
+from scoreboard import Scoreboard
+import time
+
+screen = Screen()
+screen.setup(width=600, height=600)
+screen.bgcolor("black")
+screen.title("A Snake Game!")
+screen.tracer(0)
+
+snake = Snake()
+food = Food()
+scoreboard = Scoreboard()
+
+screen.listen()
+screen.onkey(snake.up, "Up")
+screen.onkey(snake.down, "Down")
+screen.onkey(snake.left, "Left")
+screen.onkey(snake.right, "Right")
+
+game_is_on = True
+while game_is_on:
+    screen.update()
+    time.sleep(0.075)
+    snake.move()
+
+    # Food collision
+    if snake.head.distance(food) < 15:
+        food.refresh()
+        snake.extend()
+        scoreboard.increase_score()
+
+    # Wall collision
+    if (
+        snake.head.xcor() > 280
+        or snake.head.xcor() < -280
+        or snake.head.ycor() > 290
+        or snake.head.ycor() < -280
+    ):
+        scoreboard.game_over()
+        game_is_on = False
+
+    # Tail collision
+    for segment in snake.segments[1:]:
+        if snake.head.distance(segment) < 10:
+            scoreboard.game_over()
+            game_is_on = False
+
+screen.exitonclick()

Day 21/scoreboard.py

@@ -0,0 +1,28 @@
+from turtle import Turtle
+
+ALIGNMENT = "center"
+FONT = ("Open Sans", 16, "normal")
+
+
+class Scoreboard(Turtle):
+    def __init__(self):
+        super().__init__()
+        self.score = 0
+        self.penup()
+        self.hideturtle()
+        self.goto(x=0, y=260)
+        self.color("white")
+        self.update_scoreboard()
+
+    def update_scoreboard(self):
+        self.write(f"Score: {self.score}", align=ALIGNMENT, font=FONT)
+
+    def increase_score(self):
+        self.score += 1
+        self.clear()
+        self.update_scoreboard()
+
+    def game_over(self):
+        self.goto(x=0, y=0)
+        self.color("red")
+        self.write("GAME OVER", align=ALIGNMENT, font=FONT)

Day 21/snake.py

@@ -0,0 +1,53 @@
+from turtle import Turtle
+
+STARTING_POSITIONS = [(0, 0), (-20, 0), (-40, 0)]
+MOVE_DISTANCE = 20
+UP = 90
+DOWN = 270
+LEFT = 180
+RIGHT = 0
+
+
+class Snake:
+    def __init__(self):
+        self.segments = []
+        self.create_snake()
+        self.head = self.segments[0]
+
+    def create_snake(self):
+        for position in STARTING_POSITIONS:
+            self.add_segment(position)
+
+    def add_segment(self, position):
+        segment = Turtle(shape="square")
+        segment.color("white")
+        segment.penup()
+        segment.goto(position)
+        self.segments.append(segment)
+
+    def extend(self):
+        # Add a new segment to the snake.
+        self.add_segment(self.segments[-1].position())
+
+    def move(self):
+        for segment_index in range(len(self.segments) - 1, 0, -1):
+            new_x = self.segments[segment_index - 1].xcor()
+            new_y = self.segments[segment_index - 1].ycor()
+            self.segments[segment_index].goto(new_x, new_y)
+        self.head.forward(MOVE_DISTANCE)
+
+    def up(self):
+        if self.head.heading() != DOWN:
+            self.head.setheading(90)
+
+    def down(self):
+        if self.head.heading() != UP:
+            self.head.setheading(270)
+
+    def left(self):
+        if self.head.heading() != RIGHT:
+            self.head.setheading(180)
+
+    def right(self):
+        if self.head.heading() != LEFT:
+            self.head.setheading(0)