snake.rb

require "ruby2d"

set background: "navy"
set fps_cap: 20

#width = 640/20 = 32
#height = 480/20 = 24

GRID_SIZE = 20
GRID_WIDTH = Window.width/ GRID_SIZE
GRID_HEIGHT = Window.height/ GRID_SIZE


class Snake
	attr_writer :direction
	def initialize
		@positions = [[2, 0], [2, 1],[2, 2],[2, 3]]
		@direction = 'down'
		@growing = false
	end

	def draw
		@positions.each do |position|
			Square.new(x: position[0] * GRID_SIZE, y:position[1] * GRID_SIZE, size: GRID_SIZE - 1, color: 'white')
		end
	end

	def move
		if !@growing
			@positions.shift
		end
		case @direction
		when 'down'
			@positions.push(new_coords(head[0], head[1] + 1))
		when 'up'
			@positions.push(new_coords(head[0], head[1] - 1))
		when 'left'
			@positions.push(new_coords(head[0] - 1, head[1]))
		when 'right'
			@positions.push(new_coords(head[0] + 1, head[1]))
		end
		@growing = false
	end

	def can_change_direction_to?(new_direction)
		case @direction
		when 'up' then new_direction != 'down'
		when 'down' then new_direction != 'up'
		when 'left' then new_direction != 'right'
		when 'right' then new_direction != 'left'
		end
	end			

	def x
		head[0]
	end

	def y
		head[1]
	end

	def grow
		@growing = true
	end

	def hit_itself?
		@positions.uniq.length != @positions.length
	end

	private

	def new_coords(x, y)
		[x % GRID_WIDTH, y % GRID_HEIGHT]
	end


	private

	def head
		@positions.last
	end

end

class Game
	def initialize
		@score = 0
		@apple_x = rand(GRID_WIDTH)
		@apple_y = rand(GRID_HEIGHT)
		@finished = false
	end

	def draw
		unless finished?
			Square.new(x: @apple_x * GRID_SIZE, y:@apple_y * GRID_SIZE, size: GRID_SIZE, color: 'red')
		end
		Text.new(text_message, color: 'yellow', x: 10, y: 10, size: 25)
	end

	def snake_eat_food?(x,y)
		@apple_x == x && @apple_y == y
	end

	def record_hit
		@score += 1
		@apple_x = rand(GRID_WIDTH)
		@apple_y = rand(GRID_HEIGHT)
	end

	def finish
		@finished = true
	end


	def finished?
		@finished
	end

	private

	def text_message
		if finished?
			"Game Over! Your Score was #{@score}. Press R to restart."
		else
			"Score: #{@score}"
		end
	end
end

snake = Snake.new
game = Game.new

update do
	clear
	unless game.finished?
		snake.move
	end
	snake.draw
	game.draw

	if game.snake_eat_food?(snake.x, snake.y)
		game.record_hit
		snake.grow
	end	
	if snake.hit_itself?
		game.finish
	end
end

on :key_down do |event|
	if ['up', 'left', 'right', 'down'].include?(event.key)
		if snake.can_change_direction_to?(event.key)	
			snake.direction = event.key
		end
	elsif event.key == 'r'
		snake = Snake.new
		game = Game.new
	end

end
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