pong.js Example File
script/context2d/scripts/pong.js
// globals
playarea_canvas = document.getElementById('tutorial');
playarea_canvas.resize(320,200);
playarea = playarea_canvas.getContext('2d');
//p1_scr = document.getElementById('p1_scr');
//p2_scr = document.getElementById('p2_scr');
//status_msg = document.getElementById('status');
//debug = document.getElementById('debug');
ball_direction = 0;
up = -1;
down = 1;
//key codes
key_up = 38;
key_down = 40;
key_W = 87;
key_S = 83;
key_pause = 32;
speed = 2; //controls the speed of the ball
paddle_inc = 10; //how many pixels paddle can move in either direction
pause = false;
player_1 = 0; //player IDs
player_2 = 1;
player_1_scr = 0; //player scores
player_2_scr = 0;
player_1_direction = null; //null = no movement whatsoever
player_2_direction = null;
pa = new Array();
divider = new Array();
paddle_1 = new Array();
paddle_2 = new Array();
ball = new Array();
function sleep(numberMillis)
{
var now = new Date();
var exitTime = now.getTime() + numberMillis;
while (true) {
now = new Date();
if (now.getTime() > exitTime)
return;
}
}
function init()
{
pa['width'] = 150;
pa['height'] = 140;
pa['player_margin'] = 10; //area behind player paddles
pa['foreground'] = "#FFFFFF";
pa['background'] = "#000000";
divider['pos'] = pa['width']/2;
divider['width'] = 4;
paddle_1['width'] = 8;
paddle_1['height'] = 64;
paddle_1['x'] = pa['player_margin'];
paddle_1['y'] = (pa['height'] /2 ) - (paddle_1['height'] / 2);
paddle_2['width'] = 8;
paddle_2['height'] = 64;
paddle_2['x'] = (pa['width'] - pa['player_margin'] - paddle_2['width']);
paddle_2['y'] = (pa['height'] /2 ) - (paddle_2['height'] / 2);
ball['width'] = 10;
ball['height'] = 10;
ball['x'] = (pa['width']/2) - (ball['width'] / 2);
ball['y'] = (pa['height']/2) - (ball['height'] / 2);
ball_direction = Math.random() * 360; //initialize ball direction, which is determined by angle, at random
speed = 2;
}
function renderPlayarea()
{
playarea.beginPath();
playarea.clearRect(0,0,pa['width'],pa['height']);
playarea.fillStyle = pa['background'];
playarea.strokeStyle = pa['foreground'];
playarea.fillRect(0,0, pa['width'], pa['height']);
//move paddles
if(player_1_direction != null)
{
if(player_1_direction == up)
paddle_1['y'] = paddle_1['y'] - paddle_inc;
else
paddle_1['y'] = paddle_1['y'] + paddle_inc;
}
if(player_2_direction != null)
{
if(player_2_direction == up)
paddle_2['y'] = paddle_2['y'] - paddle_inc;
else
paddle_2['y'] = paddle_2['y'] + paddle_inc;
}
playarea.rect(paddle_1['x'],paddle_1['y'],paddle_1['width'],paddle_1['height']);
playarea.rect(paddle_2['x'],paddle_2['y'],paddle_2['width'],paddle_2['height']);
//move ball
playarea.rect(ball['x'], ball['y'], ball['width'], ball['height']);
ball['x'] = ball['x'] + Math.cos((ball_direction)*Math.PI/180) * speed;
ball['y'] = ball['y'] + Math.sin((ball_direction)*Math.PI/180) * speed;
playarea.fillStyle = pa['foreground'];
playarea.fill();
playarea.beginPath();
//redraw divider
playarea.lineWidth = divider['width'];
playarea.lineTo(divider['pos'], 0);
playarea.lineTo(divider['pos'], pa['height'] = 200);
playarea.lineWidth = 1;
playarea.stroke();
playarea.closePath();
}
function testCollisions()
{
//make sure paddles don't go beyond play area
if(((paddle_1['y'] <= 0) && (player_1_direction == up)) || ((paddle_1['y'] >= (pa['height'] - paddle_1['height'])) && (player_1_direction == down)))
player_1_direction = null;
if(((paddle_2['y'] <= 0) && (player_2_direction == up)) || ((paddle_2['y'] >= (pa['height'] - paddle_2['height'])) && (player_2_direction == down)))
player_2_direction = null;
//check to see if ball went beyond paddles, and if so, score accordingly and reset playarea
if(ball['x'] <= 0)
{
setScore(player_2);
init()
sleep(1000);
}
if(ball['x'] >= (pa['width'] - ball['width']))
{
setScore(player_1);
init();
sleep(1000);
}
//check to see if ball hit top or bottom wall. if so, change direction
if((ball['y'] >= (pa['height'] - ball['height'])) || ball['y'] <= 0)
ball_direction = -ball_direction;
//check to see if the ball hit a paddle, and if so, change ball angle dependant on where it hit the paddle
if((ball['x'] <= (paddle_1['x'] + paddle_1['width'])) && (ball['y'] >= paddle_1['y']) && (ball['y'] <= (paddle_1['y'] + paddle_1['height'])))
{
ball_direction = -ball_direction/2;
speed += .5;
}
if(((ball['x'] + ball['width']) >= paddle_2['x']) && (ball['y'] >= paddle_2['y']) && (ball['y'] <= (paddle_2['y'] + paddle_2['height'])))
{
ball_direction = (180+ball_direction)/2;
speed += .5;
}
}
function setScore(p)
{
if(p == player_1)
{
player_1_scr++;
//p1_scr.firstChild.nodeValue = player_1_scr;
}
if(p == player_2)
{
player_2_scr++;
//p2_scr.firstChild.nodeValue = player_2_scr;
}
}
//handle input
document.onkeydown = function(ev)
{
switch(ev.keyCode)
{
case key_W:
player_1_direction = up;
break;
case key_S:
player_1_direction = down;
break;
case key_up:
player_2_direction = up;
break;
case key_down:
player_2_direction = down;
break;
}
}
document.onkeyup = function(ev)
{
switch(ev.keyCode)
{
case key_W:
case key_S:
player_1_direction = null;
break;
case key_up:
case key_down:
player_2_direction = null;
break;
case key_pause:
if(pause == false)
{
clearInterval(game);
//status_msg.style.visibility = "visible";
pause = true;
}
else
{
game = setInterval(main, 25);
//status_msg.style.visibility = "hidden";
pause = false;
}
break;
}
}
function main()
{
testCollisions();
renderPlayarea();
}
init();
game = setInterval(main, 25);
