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-- Company:
-- Engineer:
--
-- Create Date:    14:24:57 07/31/2014
-- Design Name:
-- Module Name:    ball - Behavioral
-- Project Name:
-- Target Devices:
-- Tool versions:
-- Description:
--
-- Dependencies:
--
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
--
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity ball is

Port ( v_sync : in STD_LOGIC;
pixel_row : in STD_LOGIC_VECTOR(9 downto 0);
pixel_col : in STD_LOGIC_VECTOR(9 downto 0);
red : out STD_LOGIC;
green : out STD_LOGIC;
blue : out STD_LOGIC);
end ball;

architecture Behavioral of ball is
constant size: integer:=8;
signal ball_on: STD_LOGIC;
--indicates whether ball is over current pixel position
--current ball position-intitialized to center of screen
signal ball_x: STD_LOGIC_VECTOR(9 downto 0):= CONV_STD_LOGIC_VECTOR(320,10);
signal ball_y: STD_LOGIC_VECTOR(9 downto 0):= CONV_STD_LOGIC_VECTOR(240,10);

--current ball motion-initialized to +4 pixels/frame
signal ball_y_motion: STD_LOGIC_VECTOR(9 downto 0):= "0000001000";
signal ball_x_motion: STD_LOGIC_VECTOR(9 downto 0):= "0000001000";
begin
blue <= '1';
--color setup for red ball on white background
green <= not ball_on;
red <= not ball_on;
--process to draw ball current pixel address is covered by ball position
bdraw: process (ball_x, ball_y, pixel_row, pixel_col) is

variable bx,by,pr,pc,sz,x,y: integer;


begin
bx:=conv_integer(ball_x);
by:=conv_integer(ball_y);
pr:=conv_integer(pixel_row);
pc:=conv_integer(pixel_col);

x:=pr-bx;
y:=pc-by;

	if (size*size >= ((x*x)+(y*y))) then
		ball_on<='1';
		else
			ball_on<='0';
	end if;
--if (pixel_col >= ball_x - size) and
--	(pixel_col <=ball_x + size) and
--	(pixel_row >= ball_y - size) and
--	(pixel_row <= ball_y + size) then
--ball_on <= '1';
--else ball_on <= '0';
--end if;

end process;
--process to move ball once every frame (i.e. once every vsync pulse)
	mball: process
	begin
	wait until rising_edge(v_sync);
--allow for bounce off top or bottom of screen
		if ball_y + size >= 640 then
		ball_y_motion <= "1111111100";
		-- -4 pixels
		elsif ball_y <= size then
		ball_y_motion <= "0000000100";
		-- 		+4 pixels
		end if;
		-- Horizontal Motion
		ball_x <= ball_x + ball_x_motion;
				if ball_x + size >= 480 then
		ball_x_motion <= "1111111100";
		-- -4 pixels
		elsif ball_x <= size then
		ball_x_motion <= "0000000100";
		-- 		+4 pixels
		end if;
		ball_y <= ball_y + ball_y_motion;
		ball_x <= ball_x + ball_x_motion;
--compute next ball position
end process;
end Behavioral;