I got this game coded in Javascript:
window.onload = function() {
canv = document.getElementById("gc");
ctx = canv.getContext("2d");
document.addEventListener("keydown", keyPush);
setInterval(game, 1000 / 7);
}
px = py = 10;
gs = tc = 27;
ax = ay = 15;
xv = yv = 0;
trail = [];
tail = 2;
function game () {
px += xv;
py += yv;
if (px < 0) {
px = tc - 1;
}
if (px > tc - 1) {
px = 0;
}
if (py < 0) {
py = tc-1;
}
if (py > tc - 1) {
py = 0;
}
ctx.fillStyle = "black";
ctx.fillRect(0, 0, canv.width, canv.height);
ctx.fillStyle = "lime";
for(var i = 0; i < trail.length; i++) {
ctx.fillRect(trail[i].x * gs, trail[i].y * gs, gs - 2, gs - 2);
if (trail[i].x == px && trail[i].y == py) {
tail = 2;
}
}
trail.push({ x: px, y: py });
while(trail.length > tail) {
trail.shift();
}
if (ax == px && ay == py) {
tail++;
ax = Math.floor(Math.random() * tc);
ay = Math.floor(Math.random() * tc);
}
ctx.fillStyle = "red";
ctx.fillRect(ax * gs, ay * gs, gs - 2, gs - 2);
}
function keyPush(evt) {
switch(evt.keyCode) {
case 37:
xv = -1; yv = 0;
break;
case 38:
xv = 0; yv = -1;
break;
case 39:
xv = 1; yv = 0;
break;
case 40:
xv = 0; yv = 1;
break;
}
}
<canvas id="gc" width="729" height="729"></canvas>
And I want to add a counter anywhere on the page, so it counts how long the "tail" is.
I have tried a little myself but it doesn't seem to work, any ideas how I should do?
Also another question... how do I change the code with a button or text field on a webpage? Like for example changing:
setInterval(game,1000/7);
to
setInterval(game,1000/9);
with a button or a text field, where you can type the numbers and it gets pasted into the code?
And i want to add a counter anywhere on the page, so it counts how
long the "tail" is. I have tried a little myself but it dosen't seem
to work, any ideas how i do?
For this question, you can add an element to the page and then update it's text in javascript each time the tail changes length (using the innerText property of the element).
Sample html element:
<!-- inside the body element -->
<div>
<span>Tail Count: </span>
<span id="tail-counter">2</span>
</div>
And the javascript:
while (trail.length > tail) {
trail.shift();
document.getElementById("tail-counter").innerText = tail;
}
if (ax == px && ay == py) {
tail++;
document.getElementById("tail-counter").innerText = tail;
ax = Math.floor(Math.random() * tc);
ay = Math.floor(Math.random() * tc);
}
Also another queston... how do i change the code with a button or text
field on a webpage? Like for example changing
setInterval(game,1000/7); to setInterval(game,1000/9); with a button
or a text field, where you can type the numbers and it gets pasted
into the code?
For this question, to change the code based on a text field, you need to first add the text field to the page:
<div>
<span>Set Game Speed: </span>
<input id="game-speed" type="number" value="7" />
</div>
Then you can use javascript to get the value of the text field and use it in your code
game_speed = Number.parseInt(document.getElementById("game-speed").value);
interval = setInterval(game, 1000 / game_speed);
Now all together (note that this code allows you to change the game speed while playing. This is done by clearing the interval you already made with clearInterval and then setting a new interval with the new game speed)
<canvas id="gc" width="729" height="729"></canvas>
<body style="overflow-x: hidden; overflow-y: hidden;">
<div>
<span>Tail Count: </span>
<span id="tail-counter">2</span>
</div>
<div>
<span>Set Game Speed: </span>
<input id="game-speed" type="number" value="7" />
</div>
</body>
<script>
px = py = 10;
gs = tc = 27;
ax = ay = 15;
xv = yv = 0;
trail = [];
tail = 2;
game_speed = 7;
interval = {};
window.onload = function () {
canv = document.getElementById("gc");
ctx = canv.getContext("2d");
document.addEventListener("keydown", keyPush);
game_speed = Number.parseInt(document.getElementById("game-speed").value);
interval = setInterval(game, 1000 / game_speed);
}
function game() {
let new_speed = Number.parseInt(document.getElementById("game-speed").value);
if (new_speed !== game_speed) {
clearInterval(interval);
game_speed = new_speed;
interval = setInterval(game, 1000 / game_speed);
}
px += xv;
py += yv;
if (px < 0) {
px = tc - 1;
}
if (px > tc - 1) {
px = 0;
}
if (py < 0) {
py = tc - 1;
}
if (py > tc - 1) {
py = 0;
}
ctx.fillStyle = "black";
ctx.fillRect(0, 0, canv.width, canv.height);
ctx.fillStyle = "lime";
for (var i = 0; i < trail.length; i++) {
ctx.fillRect(trail[i].x * gs, trail[i].y * gs, gs - 2, gs - 2);
if (trail[i].x == px && trail[i].y == py) {
tail = 2;
}
}
trail.push({
x: px,
y: py
});
while (trail.length > tail) {
trail.shift();
document.getElementById("tail-counter").innerText = tail;
}
if (ax == px && ay == py) {
tail++;
document.getElementById("tail-counter").innerText = tail;
ax = Math.floor(Math.random() * tc);
ay = Math.floor(Math.random() * tc);
}
ctx.fillStyle = "red";
ctx.fillRect(ax * gs, ay * gs, gs - 2, gs - 2);
}
function keyPush(evt) {
switch (evt.keyCode) {
case 37:
xv = -1;
yv = 0;
break;
case 38:
xv = 0;
yv = -1;
break;
case 39:
xv = 1;
yv = 0;
break;
case 40:
xv = 0;
yv = 1;
break;
}
}
</script>
<html>
To use predefined value as you setInterval timer, all you need to do is to find your best method of getting user inputs, e.g using an input box. Then you can grab the value with javascript
E.g
[HTML]
<input type="number" value="500" id="num">
[JS]
let num = document.getElementById('num').value;
num = +num; //cast the value to number since its returned as a string.
setInterval(game, num/nth); //nth is any value of your choice, or you can also grab from user input
```
For your first question, getting how long the tail is depends on how you want it.
you can use a variable and always increment it, each time your code condition is met.
In order to write the trail length in the canvas, I added to your code
ctx.fillStyle = "blue";
ctx.fillText(trail.length, 100, 100);
ctx.font = "bold 20px sans-serif";
ctx.textBaseline = "bottom";
that way it constantly prints the trail length at the top left corner.
and as for your second question, I added the intervalTime variable at the global scope so you could change it and then the next interval will be in the time you entered to that variable.
var intervalTime = 1000/7;
window.onload=function() {
canv=document.getElementById("gc");
ctx=canv.getContext("2d");
document.addEventListener("keydown",keyPush);
setInterval(game, intervalTime);
}
px=py=10;
gs=tc=27;
ax=ay=15;
xv=yv=0;
trail=[];
tail = 2;
function game() {
px+=xv;
py+=yv;
if(px<0) {
px= tc-1;
}
if(px>tc-1) {
px= 0;
}
if(py<0) {
py= tc-1;
}
if(py>tc-1) {
py= 0;
}
ctx.fillStyle="black";
ctx.fillRect(0,0,canv.width,canv.height);
ctx.fillStyle = "blue";
ctx.fillText(trail.length, 100, 100);
ctx.font = "bold 20px sans-serif";
ctx.textBaseline = "bottom";
ctx.fillStyle="lime";
for(var i=0;i<trail.length;i++) {
ctx.fillRect(trail[i].x*gs,trail[i].y*gs,gs-2,gs-2);
if(trail[i].x==px && trail[i].y==py) {
tail = 2;
}
}
trail.push({x:px,y:py});
while(trail.length>tail) {
trail.shift();
}
if(ax==px && ay==py) {
tail++;
ax=Math.floor(Math.random()*tc);
ay=Math.floor(Math.random()*tc);
}
ctx.fillStyle="red";
ctx.fillRect(ax*gs,ay*gs,gs-2,gs-2);
}
function keyPush(evt) {
switch(evt.keyCode) {
case 37:
xv=-1;yv=0;
break;
case 38:
xv=0;yv=-1;
break;
case 39:
xv=1;yv=0;
break;
case 40:
xv=0;yv=1;
break;
}
}
<canvas id="gc" width="729" height="729"></canvas>
Related
I have gotten the part where when the ball collides with the block it deletes the block, but I am also wanting to tell if the ball hits the top or bottom or left or right of the block and bounce accordingly. I have attempted it, but it's not working quite right. It just freaks out jumping around. I have deleted that portion from the code below as it does not work. Can anyone help me out with this problem? Maybe give an example or tell me how it would work?
<canvas id="can" height="500" width="1000"></canvas>
var c = document.getElementById("can");
var ctx = c.getContext("2d");
var blocks= [];
var paddle = {x:450,y:480,h:10,w:100};
var ball = {r:7,x:500,y:469};
var rows=[0,1,2,3,4];
var px = paddle.x, py = paddle.y;
var pxv=0;
var by = ball.y, bx = ball.x;
var bxv = -1.5, byv = -1.5;
function Block(h,w,x,y,c) {
this.h = h;
this.w = w;
this.x = x;
this.y = y;
this.c = c;
}
for(var i =0, len=rows.length;i<len;i++){
for(var j=0; j<20;j++) {
blocks.push(new Block(20,50,j*50,i*20,rows[i]))
}
}
document.addEventListener("keydown",keyPush);
document.addEventListener("keyup",keyRelease);
function keyRelease(evt) {
switch(evt.keyCode) {
case 37:
pxv=0;
break;
case 39:
pxv=0;
break;
}
}
function keyPush(evt) {
switch(evt.keyCode) {
case 37:
pxv=-5;
break;
case 39:
pxv=5
break;
}
}
function AABBIntersect(ax, ay, aw, ah, bx, by, bw, bh) {
return ax < bx+bw && bx < ax+aw && ay < by+bh && by < ay+ah;
};
function draw(){
ctx.clearRect(0,0,1000,500)
bx+=bxv;
by+=byv;
px+=pxv;
if(px > 900) {
px = 900;
}
else if(px < 0) {
px = 0;
}
for(var i = 0, len=blocks.length;i<len;i++) {
var bl = blocks[i];
if(AABBIntersect(bx,by,ball.r,ball.r,bl.x,bl.y,bl.w,bl.h)) {
blocks.splice(i,1);
i--;
len--;
}
}
if(bx < 0) {
bxv = bxv*-1;
}
if(bx > 1000) {
bxv = bxv*-1;
}
ctx.fillStyle = "#ff4b38"
ctx.fillRect(px,py,paddle.w,paddle.h);
for(var i = 0, len=blocks.length; i<len; i++){
if(blocks[i].c === 0) {
ctx.fillStyle = "#ff4b38"
}
else if(blocks[i].c === 1) {
ctx.fillStyle = "#ffba19"
}
else if(blocks[i].c === 2) {
ctx.fillStyle = "#fcee25"
}
else if(blocks[i].c === 3) {
ctx.fillStyle = "#26db02"
}
else if(blocks[i].c === 4) {
ctx.fillStyle = "#2d69ff"
}
ctx.fillRect(blocks[i].x,blocks[i].y,blocks[i].w,blocks[i].h);
ctx.beginPath();
ctx.arc(bx,by,ball.r,0,2*Math.PI,false);
ctx.fillStyle = "gray";
ctx.fill();
}
}
setInterval(draw,10);
I'm sure there are more ways to do it but this is how I would do it.
Inside your collision detection function you should have if-statements to detect if from the x or y side. You made need to tweak it as not sure if it will error later but the brunt of it all is like this:
function AABBIntersect(ax, ay, aw, ah, bx, by, bw, bh) {
var bool = ax < bx + bw && bx < ax + aw && ay < by + bh && by < ay + ah;
if(bool){
if(ax == bx || ax == bx + bw){
bxv *= -1;
cl("x");
}else{
byv *= -1;
cl("y");
}
}
return bool;
};
Your next issue is you have no paddle collision detection, so it will bounce back but it will go through your paddle. So you can do the following in your draw() function. I put it after your if(bx > 1000):
if(bx >= px && bx <= px + paddle.w && by >= py && by <= py + paddle.h){
byv *= -1;
}
I would also put your setInterval on a var so you can clear it when either all the blocks are gone or your ball goes below the paddle. Otherwise it's just going to go everywhere infinitely.
I am developing a animation in javascript where a car moves towards a person and picks but currently instead of a path I am just driving diagonally to the person with below code.
Car.prototype.main = function() {
var angle = angleBetweenTwoPoints(this.target.position, this.position);
var cos = Math.cos(degreeToRadian(angle)) * -1;
var sin = Math.sin(degreeToRadian(angle));
var _this = _super.call(this) || this;
this.angle = angle;
this.position.x += cos * this.speed;
this.position.y -= sin * this.speed;
if (distance(this.position, this.target.position) < 10 && this.image == GameImage.getImage("hero") ) {
this.target.position.x = Math.random() * mainCanvas.width;
this.target.position.y = Math.random() * mainCanvas.height;
this.hitCount++;
console.log(hitCount);
ctx.fillText("points : " + hitCount, 32, 32);
this.changeImage = true;
_this.speed = 3;
this.changeImageTime = Date.now() + 600; //0.5 sec from now.
this.image = (this.image == GameImage.getImage("hero"))? GameImage.getImage("hero_other") : GameImage.getImage("hero");
}
if(this.changeImage){
if(Date.now() > this.changeImageTime){
this.changeImage = false;
_this.speed = 9;
this.image = (this.image == GameImage.getImage("hero_other"))? GameImage.getImage("hero") : GameImage.getImage("hero_other");
}
}
};
return Car;
}(Actor));
But instaed of this I want to follow a path.I also created some grids when u click the image it logs the console which grid it is.But I am unable move the car in a path.For complete understanding the animation is in
animation.
Any help is appreciated
Waypoints as a queue.
For waypoints path following you use a type of array called a queue. As the name suggests the queue holds items that need to be used, specifically they need to be used in the order in which they arrive. The first object on the queue is the first object out (unless you push in line)
In javascript a queue is easy to implement using an array.
const path = {
points : [],
currentPos : null,
dist : 0,
totalDistMoved : 0,
atEnd : false,
addPoint(x,y) {
if(this.currentPos === null){
this.currentPos = { x :0,y : 0};
this.dist = 0;
this.totalDistMoved = 0;
}
this.points.push({x,y}) ;
},
moveAlong(dist){
if(dist > 0){
if(this.points.length > 1){
var x = this.points[1].x - this.points[0].x;
var y = this.points[1].y - this.points[0].y;
var len = Math.sqrt(x*x+y*y) ;
if(len - this.dist < dist){
this.points.shift();
dist -= (len - this.dist);
this.totalDistMoved += (len - this.dist);
this.dist = 0;
this.moveAlong(dist);
return;
}
const frac = this.dist + dist / len;
this.currentPos.x = this.points[0].x + x * frac;
this.currentPos.y = this.points[0].y + y * frac;
this.dist += dist;
this.totalDistMoved += dist;
}else{
this.currentPos.x = this.points[0].x;
this.currentPos.y = this.points[0].y;
this.dist = 0;
this.atEnd = true;
}
}
}
}
To use
Add some way points.
path.addPoint(1,1);
path.addPoint(100,20);
path.addPoint(110,120);
path.addPoint(210,120);
path.addPoint(250,420);
Then for each step of the animations get a distance along
path.moveAlong(10); // move ten pixels
and use the current position
ctx.drawImage(car,path.currentPos.x,path.currentPos.y);
You know you have reached the end of the path when.
if(path.atEnd) {
// you have arrived
}
And at any time you know how far you have moved with
path.totalDistMoved
This is meant for animations that only play forward. It will ignore negative distances as way points are dumped when you have passed them
You will need to make some modifications if you wish to reuse the path object, or if the waypoints are being added as you go
A simple example.
Thing moves along at constant speed. Click on page to add more waypoints.
const ctx = canvas.getContext("2d");
requestAnimationFrame(mainLoop);
function mainLoop(time){
gTime = !gTime ? time : gTime;
fTime = time - gTime;
gTime = time;
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
}else{
ctx.setTransform(1,0,0,1,0,0);
ctx.clearRect(0,0,canvas.width,canvas.height);
}
if(mouse.button){
if(!point){
point = {x:0,y:0};
path.addPoint(point);
}
point.x = mouse.x;
point.y = mouse.y;
}else{
if(point){ point = null }
}
ctx.beginPath();
var i = 0;
while(i < path.points.length){ ctx.lineTo(path.points[i].x,path.points[i++].y)}
ctx.strokeStyle = "blue";
ctx.lineWidth = 2;
ctx.stroke();
var i = 0;
while(i < path.points.length){ ctx.strokeRect(path.points[i].x-4,path.points[i++].y-4,8,8)}
path.moveAlong(4 * fTime / 100);
var x = path.currentPos.x - thingPos.x;
var y = path.currentPos.y - thingPos.y;
thingPos.x = path.currentPos.x;
thingPos.y = path.currentPos.y;
drawThing(thingPos.x,thingPos.y,Math.atan2(y,x));
requestAnimationFrame(mainLoop);
}
var point;
const thingPos = {x:0,y:0};
const path = {
points : [],
currentPos : null,
distAlong : 0,
totalDistMoved : 0,
atEnd : false,
addPoint(x,y) {
if(y === undefined){
this.points.push(x); // add point as object
return;
}
if(this.currentPos === null){
this.currentPos = { x :0,y : 0};
this.distAlong = 0;
this.totalDistMoved = 0;
}
this.points.push({x,y}) ;
},
moveAlong(dist){
if(dist > 0){
if(this.points.length > 1){
var x = this.points[1].x - this.points[0].x;
var y = this.points[1].y - this.points[0].y;
var len = Math.sqrt(x*x+y*y) ;
if(len - this.distAlong < dist){
this.points.shift();
dist -= (len - this.distAlong);
this.totalDistMoved += (len - this.distAlong);
this.distAlong = 0;
this.moveAlong(dist);
return;
}
const frac = (this.distAlong + dist) / len;
this.currentPos.x = this.points[0].x + x * frac;
this.currentPos.y = this.points[0].y + y * frac;
this.distAlong += dist;
this.totalDistMoved += dist;
}else{
this.currentPos.x = this.points[0].x;
this.currentPos.y = this.points[0].y;
this.distAlong = 0;
this.atEnd = true;
}
}
}
}
path.addPoint(20,20);
path.addPoint(120,20);
path.addPoint(220,120);
path.addPoint(320,120);
path.addPoint(420,20);
function mouseEvents(e) {
const m = mouse;
m.x = e.pageX;
m.y = e.pageY;
m.button = e.type === "mousemove" ? m.button : e.type === "mousedown";
}
function drawThing(x,y,dir) {
ctx.setTransform(1,0,0,1,x,y);
ctx.rotate(dir);
ctx.fillStyle = "red";
ctx.strokeStyle = "black";
ctx.lineWidth = 2;
ctx.beginPath();
var i = 0;
while(i < thing.length){ ctx.lineTo(thing[i++],thing[i++]) };
ctx.closePath();
ctx.fill();
ctx.stroke();
}
const thing = [-20,-10,20,-10,22,-7,22,7,20,10,-20,10];
var gTime; // global and frame time
var fTime;
const mouse = { x:0,y:0,button:false};
["mousemove","mousedown","mouseup"].forEach(t=>document.addEventListener(t,mouseEvents));
canvas {
position: absolute;
top : 0px;
left : 0px;
}
<canvas id="canvas"></canvas>
click drag to add waypoints.
I'm trying to get this particle explosion working. It's working but it looks like some frames does not get rendered. If I click many times to call several explosions it starts to uhm.. "lag/stutter". Is there something I have forgotten to do? It may look like the browser hangs when I click many times. Is it too much to have 2 for loops inside each other?
Attached my code so you can see.
Just try to click many times, and you will see the problem visually.
// Request animation frame
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
// Canvas
var c = document.getElementById('canvas');
var ctx = c.getContext('2d');
// Set full-screen
c.width = window.innerWidth;
c.height = window.innerHeight;
// Options
var background = '#333'; // Background color
var particlesPerExplosion = 20;
var particlesMinSpeed = 3;
var particlesMaxSpeed = 6;
var particlesMinSize = 1;
var particlesMaxSize = 3;
var explosions = [];
var fps = 60;
var now, delta;
var then = Date.now();
var interval = 1000 / fps;
// Optimization for mobile devices
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)) {
fps = 29;
}
// Draw
function draw() {
// Loop
requestAnimationFrame(draw);
// Set NOW and DELTA
now = Date.now();
delta = now - then;
// New frame
if (delta > interval) {
// Update THEN
then = now - (delta % interval);
// Our animation
drawBackground();
drawExplosion();
}
}
// Draw explosion(s)
function drawExplosion() {
if (explosions.length == 0) {
return;
}
for (var i = 0; i < explosions.length; i++) {
var explosion = explosions[i];
var particles = explosion.particles;
if (particles.length == 0) {
explosions.splice(i, 1);
return;
}
for (var ii = 0; ii < particles.length; ii++) {
var particle = particles[ii];
// Check particle size
// If 0, remove
if (particle.size < 0) {
particles.splice(ii, 1);
return;
}
ctx.beginPath();
ctx.arc(particle.x, particle.y, particle.size, Math.PI * 2, 0, false);
ctx.closePath();
ctx.fillStyle = 'rgb(' + particle.r + ',' + particle.g + ',' + particle.b + ')';
ctx.fill();
// Update
particle.x += particle.xv;
particle.y += particle.yv;
particle.size -= .1;
}
}
}
// Draw the background
function drawBackground() {
ctx.fillStyle = background;
ctx.fillRect(0, 0, c.width, c.height);
}
// Clicked
function clicked(e) {
var xPos, yPos;
if (e.offsetX) {
xPos = e.offsetX;
yPos = e.offsetY;
} else if (e.layerX) {
xPos = e.layerX;
yPos = e.layerY;
}
explosions.push(new explosion(xPos, yPos));
}
// Explosion
function explosion(x, y) {
this.particles = [];
for (var i = 0; i < particlesPerExplosion; i++) {
this.particles.push(new particle(x, y));
}
}
// Particle
function particle(x, y) {
this.x = x;
this.y = y;
this.xv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.yv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.size = randInt(particlesMinSize, particlesMaxSize, true);
this.r = randInt(113, 222);
this.g = '00';
this.b = randInt(105, 255);
}
// Returns an random integer, positive or negative
// between the given value
function randInt(min, max, positive) {
if (positive == false) {
var num = Math.floor(Math.random() * max) - min;
num *= Math.floor(Math.random() * 2) == 1 ? 1 : -1;
} else {
var num = Math.floor(Math.random() * max) + min;
}
return num;
}
// On-click
$('canvas').on('click', function(e) {
clicked(e);
});
draw();
<!DOCTYPE html>
<html>
<head>
<style>
* {
margin: 0;
padding: 0;
overflow: hidden;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
</body>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
</html>
You are returning from iterating over the particles if one is too small. This causes the other particles of that explosion to render only in the next frame.
I have a working version:
// Request animation frame
const requestAnimationFrame = window.requestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.msRequestAnimationFrame;
// Canvas
const c = document.getElementById('canvas');
const ctx = c.getContext('2d');
// Set full-screen
c.width = window.innerWidth;
c.height = window.innerHeight;
// Options
const background = '#333'; // Background color
const particlesPerExplosion = 20;
const particlesMinSpeed = 3;
const particlesMaxSpeed = 6;
const particlesMinSize = 1;
const particlesMaxSize = 3;
const explosions = [];
let fps = 60;
const interval = 1000 / fps;
let now, delta;
let then = Date.now();
// Optimization for mobile devices
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)) {
fps = 29;
}
// Draw
function draw() {
// Loop
requestAnimationFrame(draw);
// Set NOW and DELTA
now = Date.now();
delta = now - then;
// New frame
if (delta > interval) {
// Update THEN
then = now - (delta % interval);
// Our animation
drawBackground();
drawExplosion();
}
}
// Draw explosion(s)
function drawExplosion() {
if (explosions.length === 0) {
return;
}
for (let i = 0; i < explosions.length; i++) {
const explosion = explosions[i];
const particles = explosion.particles;
if (particles.length === 0) {
explosions.splice(i, 1);
return;
}
const particlesAfterRemoval = particles.slice();
for (let ii = 0; ii < particles.length; ii++) {
const particle = particles[ii];
// Check particle size
// If 0, remove
if (particle.size <= 0) {
particlesAfterRemoval.splice(ii, 1);
continue;
}
ctx.beginPath();
ctx.arc(particle.x, particle.y, particle.size, Math.PI * 2, 0, false);
ctx.closePath();
ctx.fillStyle = 'rgb(' + particle.r + ',' + particle.g + ',' + particle.b + ')';
ctx.fill();
// Update
particle.x += particle.xv;
particle.y += particle.yv;
particle.size -= .1;
}
explosion.particles = particlesAfterRemoval;
}
}
// Draw the background
function drawBackground() {
ctx.fillStyle = background;
ctx.fillRect(0, 0, c.width, c.height);
}
// Clicked
function clicked(e) {
let xPos, yPos;
if (e.offsetX) {
xPos = e.offsetX;
yPos = e.offsetY;
} else if (e.layerX) {
xPos = e.layerX;
yPos = e.layerY;
}
explosions.push(
new explosion(xPos, yPos)
);
}
// Explosion
function explosion(x, y) {
this.particles = [];
for (let i = 0; i < particlesPerExplosion; i++) {
this.particles.push(
new particle(x, y)
);
}
}
// Particle
function particle(x, y) {
this.x = x;
this.y = y;
this.xv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.yv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.size = randInt(particlesMinSize, particlesMaxSize, true);
this.r = randInt(113, 222);
this.g = '00';
this.b = randInt(105, 255);
}
// Returns an random integer, positive or negative
// between the given value
function randInt(min, max, positive) {
let num;
if (positive === false) {
num = Math.floor(Math.random() * max) - min;
num *= Math.floor(Math.random() * 2) === 1 ? 1 : -1;
} else {
num = Math.floor(Math.random() * max) + min;
}
return num;
}
// On-click
$('canvas').on('click', function (e) {
clicked(e);
});
draw();
<!DOCTYPE html>
<html>
<head>
<style>* {margin:0;padding:0;overflow:hidden;}</style>
</head>
<body>
<canvas id="canvas"></canvas>
</body>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
</html>
Loops, break and continue.
The problem was caused when you checked for empty particle arrays and when you found a particle to remove.
The bugs
The following two statements and blocks caused the problem
if (particles.length == 0) {
explosions.splice(i, 1);
return;
}
and
if (particles.size < 0) {
explosions.splice(ii, 1);
return;
}
The returns stopped the rendering of particles, so you would sometimes return before drawing a single particle was rendered just because the first explosion was empty or first particle was too small.
Continue and break
You can use the continue token in javascript to skip the rest of a for, while, do loop
for(i = 0; i < 100; i++){
if(test(i)){
// need to skip this iteration
continue;
}
// more code
// more code
// continue skips all the code upto the closing }
} << continues to here and if i < 100 the loop continues on.
Or you can completely break out of the loop with break
for(i = 0; i < 100; i++){
if(test(i)){
// need to exit the for loop
break;
}
// more code
// more code
// break skips all the code to the first line after the closing }
}
<< breaks to here and if i remains the value it was when break was encountered
The fix
if (particles.length == 0) {
explosions.splice(i, 1);
continue;
}
and
if (particles.size < 0) {
explosions.splice(ii, 1);
continue;
}
Your example with the fix
Your code with the fix. Befor I found it I started changing stuff.
Minor stuff.
requestAnimationFrame passes a time in milliseconds so to an accuracy of micro seconds.
You were setting then incorrectly and would have been losing frames. I changed the timing to use the argument time and then is just set to the time when a frame is drawn.
There are some other issues, nothing major and more of a coding style thing. You should capitalise objects created with new
function Particle(...
not
function particle(...
and your random is a overly complex
function randInt(min, max = min - (min = 0)) {
return Math.floor(Math.random() * (max - min) + min);
}
or
function randInt(min,max){
max = max === undefined ? min - (min = 0) : max;
return Math.floor(Math.random() * (max - min) + min);
}
randInt(100); // int 0 - 100
randInt(10,20); // int 10-20
randInt(-100); // int -100 to 0
randInt(-10,20); // int -10 to 20
this.xv = randInt(-particlesMinSpeed, particlesMaxSpeed);
this.yv = randInt(-particlesMinSpeed, particlesMaxSpeed);
this.size = randInt(particlesMinSize, particlesMaxSize);
And if you are using the same name in variables a good sign to create an object
var particlesPerExplosion = 20;
var particlesMinSpeed = 3;
var particlesMaxSpeed = 6;
var particlesMinSize = 1;
var particlesMaxSize = 3;
Could be
const settings = {
particles : {
speed : {min : 3, max : 6 },
size : {min : 1 : max : 3 },
explosionCount : 20,
},
background : "#000",
}
Anyways your code.
var c = canvas;
var ctx = c.getContext('2d');
// Set full-screen
c.width = innerWidth;
c.height = innerHeight;
// Options
var background = '#333'; // Background color
var particlesPerExplosion = 20;
var particlesMinSpeed = 3;
var particlesMaxSpeed = 6;
var particlesMinSize = 1;
var particlesMaxSize = 3;
var explosions = [];
var fps = 60;
var now, delta;
var then = 0; // Zero start time
var interval = 1000 / fps;
// Optimization for mobile devices
if (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)) {
fps = 29;
}
// Draw
// as time is passed you need to start with requestAnimationFrame
requestAnimationFrame(draw);
function draw(time) { //requestAnimationFrame frame passes the time
requestAnimationFrame(draw);
delta = time - then;
if (delta > interval) {
then = time
drawBackground();
drawExplosion();
}
}
// Draw explosion(s)
function drawExplosion() {
if (explosions.length == 0) {
return;
}
for (var i = 0; i < explosions.length; i++) {
var explosion = explosions[i];
var particles = explosion.particles;
if (particles.length == 0) {
explosions.splice(i, 1);
//return;
continue;
}
for (var ii = 0; ii < particles.length; ii++) {
var particle = particles[ii];
// Check particle size
// If 0, remove
if (particle.size < 0) {
particles.splice(ii, 1);
// return;
continue;
}
ctx.beginPath();
ctx.arc(particle.x, particle.y, particle.size, Math.PI * 2, 0, false);
ctx.closePath();
ctx.fillStyle = 'rgb(' + particle.r + ',' + particle.g + ',' + particle.b + ')';
ctx.fill();
// Update
particle.x += particle.xv;
particle.y += particle.yv;
particle.size -= .1;
}
}
}
// Draw the background
function drawBackground() {
ctx.fillStyle = background;
ctx.fillRect(0, 0, c.width, c.height);
}
// Clicked
function clicked(e) {
var xPos, yPos;
if (e.offsetX) {
xPos = e.offsetX;
yPos = e.offsetY;
} else if (e.layerX) {
xPos = e.layerX;
yPos = e.layerY;
}
explosions.push(new explosion(xPos, yPos));
}
// Explosion
function explosion(x, y) {
this.particles = [];
for (var i = 0; i < particlesPerExplosion; i++) {
this.particles.push(new particle(x, y));
}
}
// Particle
function particle(x, y) {
this.x = x;
this.y = y;
this.xv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.yv = randInt(particlesMinSpeed, particlesMaxSpeed, false);
this.size = randInt(particlesMinSize, particlesMaxSize, true);
this.r = randInt(113, 222);
this.g = '00';
this.b = randInt(105, 255);
}
// Returns an random integer, positive or negative
// between the given value
function randInt(min, max, positive) {
if (positive == false) {
var num = Math.floor(Math.random() * max) - min;
num *= Math.floor(Math.random() * 2) == 1 ? 1 : -1;
} else {
var num = Math.floor(Math.random() * max) + min;
}
return num;
}
// On-click
$('canvas').on('click', function(e) {
clicked(e);
});
<!DOCTYPE html>
<html>
<head>
<style>
* {
margin: 0;
padding: 0;
overflow: hidden;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
</body>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
</html>
OK, so I'm new to JS, so am trying to make the basic 'breakout' game. What I'm trying to do is arrange the bricks into a triangle shape (or more accurately, forming a triangle out of the absence of bricks). But when I choose which items in the 2D array I want to equal 0 (no brick), it only allows me choose one. after that, the game simply won't load.
Weirdest thing is, it will only accept the first line in this part. No matter what I change, the second line onwards will cause the game to not load:
bricks[0][10]=0;
bricks[7][16]=0;
bricks[7][15]=0;
bricks[7][14]=0;
bricks[7][13]=0;
bricks[7][12]=0;
bricks[7][11]=0;
bricks[7][10]=0;
bricks[7][9]=0;
bricks[7][8]=0;
bricks[7][7]=0;
bricks[7][6]=0;
bricks[7][5]=0;
bricks[7][4]=0;
bricks[7][3]=0;
bricks[7][17]=0;
bricks[6][4]=0;
bricks[6][16]=0;
bricks[5][15]=0;
bricks[5][5]=0;
bricks[4][14]=0;
bricks[4][6]=0;
bricks[3][13]=0;
bricks[3][7]=0;
bricks[2][8]=0;
bricks[2][12]=0;
bricks[1][11]=0;
bricks[1][9]=0;
Also, i know the code is incomplete and flawed as it is. It's not finished and still need a lot of polishing up.
Here's my entire code
canvasApp();
function canvasApp(){
var canvas=document.getElementById("canvas")
if (!canvas || !canvas.getContext){
return;
}
var ctx = canvas.getContext("2d");
if (!ctx) {
return
}
//Application States
const GAME_STATE_TITLE = 0;
const GAME_STATE_NEW_LEVEL = 1;
const GAME_STATE_GAME_OVER = 2;
var currentGameState = 0;
var currentGameStateFunction = null;
var brickcount;
var bouncecount = 0;
//Initialise Start Screen State
var titleStarted = false;
var gameStarted = false;
var gameOver = false;
var keyPressList = [];
var keys = false //mouse or keys. false = mouse control, vice versa
var difficulty = 0;
// Declarations for the game
var dx = 6;
var dy = 6;
var x = 150;
var y = 100;
var r = 10;
var WIDTH = 500;
var HEIGHT = 400;
var ballx = 200;
var bally = 200;
var paddlex = WIDTH/1.2;
var paddleh = 10;
var paddlew = 75;
var paddledx = 30
var mouseX;
var bricks;
var NROWS;
var NCOLS;
var BRICKWIDTH;
var BRICKHEIGHT;
var PADDING;
var rowcolours = ["#FF1C0A", "#FFFD0A", "#00A308", "#0008DB", "#EB0093"];
var paddlecolour = "#FF00FF";
var ballcolour = "#00FFFF";
var backcolour = "#0000FF";
function initbricks() {
NROWS = 9
NCOLS = 21
brickcount = NROWS*NCOLS;
BRICKWIDTH = (WIDTH/NCOLS) - 1;
BRICKHEIGHT = 10;
PADDING = 1;
bricks = new Array(NROWS);
for (i=0; i < NROWS; i++) {
bricks[i] = new Array(NCOLS);
for (j=0; j < NCOLS; j++) {
bricks[i][j] = 1;
}
bricks[0][10]=0;
bricks[7][16]=0;
bricks[7][15]=0;
bricks[7][14]=0;
bricks[7][13]=0;
bricks[7][12]=0;
bricks[7][11]=0;
bricks[7][10]=0;
bricks[7][9]=0;
bricks[7][8]=0;
bricks[7][7]=0;
bricks[7][6]=0;
bricks[7][5]=0;
bricks[7][4]=0;
bricks[7][3]=0;
bricks[7][17]=0;
bricks[6][4]=0;
bricks[6][16]=0;
bricks[5][15]=0;
bricks[5][5]=0;
bricks[4][14]=0;
bricks[4][6]=0;
bricks[3][13]=0;
bricks[3][7]=0;
bricks[2][8]=0;
bricks[2][12]=0;
bricks[1][11]=0;
bricks[1][9]=0;
}
}
initbricks();
function switchGameState(newState) {
currentGameState = newState;
switch (currentGameState) {
case GAME_STATE_TITLE:
currentGameStateFunction = gameStateTitle;
break;
case GAME_STATE_NEW_LEVEL:
currentGameStateFunction = gameStatePlayLevel;
break;
case GAME_STATE_GAME_OVER:
currentGameStateFunction = gameStateGameOver;
break;
}
}
function gameStateTitle(){
if (titleStarted != true){
ctx.fillStyle = '#000000';
ctx.fillRect(0,0,500,400);
ctx.fillStyle = '#ffffff';
ctx.font = '20px _sans';
ctx.textBaseline = 'top';
ctx.fillText ("Breakout!", 200,150);
ctx.fillText ("Press Space to Play", 170,200);
if (keys == 0 ) {
ctx.fillText ("Mouse selected", 180,250);
ctx.fillText ("Press k to switch to keys", 140,300);
} else {
ctx.fillText ("Keys selected", 190,250);
ctx.fillText ("Press m to switch to mouse", 140,300);
}
titleStarted = true;
}else{
if (keyPressList[75] == true){
keys = 1;
titleStarted = false;
gameStateTitle(); // Redraw the title page
}
if (keyPressList[77] == true){
keys = 0;
titleStarted = false;
gameStateTitle();
}
if (keyPressList[32] == true){
switchGameState(GAME_STATE_NEW_LEVEL);
titleStarted = false;
}
}
}
function gameStatePlayLevel(){
ctx.fillStyle = '#000000';
ctx.fillRect(0,0,500,400);
ctx.fillStyle = '#ffffff';
// Update the game state and check for game over
function update() {
x+=dx
y+=dy
if (keys == 0) {
paddlex = mouseX;
}else{
if (keyPressList[37]==true){
paddlex-=paddledx;
}
if (keyPressList[39]==true){
paddlex+=paddledx;
}
}
//have we hit a brick?
rowheight = BRICKHEIGHT + PADDING;
colwidth = BRICKWIDTH + PADDING;
row = Math.floor(y/rowheight);
col = Math.floor(x/colwidth);
//if so, reverse the ball and mark the brick as broken
if (y < NROWS * rowheight && row >= 0 && col >= 0 && bricks[row][col] == 1) {
dy = -dy;
bricks[row][col] = 0;
brickcount--;
if (brickcount == 0) {
switchGameState(GAME_STATE_NEW_LEVEL);
difficulty+=1;
initbricks();
x=250;
y=200 + (difficulty*20);
brickcount=NROWS*NCOLS;
bouncecount=0;
}
}
if( x<0 || x>WIDTH) dx=-dx;
if( y<0 || y>HEIGHT) dy=-dy;
else if (y + dy > HEIGHT) {
if (x > paddlex && x < paddlex + paddlew) {
dx = 8 * ((x-(paddlex+paddlew/2))/paddlew);
dy = -dy;
bouncecount++;
}
else {
//game over, so stop the animation
switchGameState(GAME_STATE_GAME_OVER);
initbricks();
}
}
}
function render() {
ctx.save();
function circle(x,y,r) {
ctx.beginPath();
ctx.arc(x, y, r, 0, Math.PI*2, true);
ctx.fill();
}
function rect(x,y,w,h) {
ctx.beginPath();
ctx.rect(x,y,w,h);
ctx.closePath();
ctx.fill();
ctx.stroke();
}
//draw bricks
for (i=0; i < NROWS; i++) {
ctx.fillStyle = rowcolours [i];
for (j=0; j < NCOLS; j++) {
if (bricks[i][j] == 1) {
rect((j * (BRICKWIDTH + PADDING)) + PADDING,
(i * (BRICKHEIGHT + PADDING)) + PADDING, BRICKWIDTH, BRICKHEIGHT);
}
}
}
circle(x, y, 10);
// init_paddle();
ctx.fillStyle = paddlecolour;
rect (paddlex, HEIGHT-paddleh, paddlew, paddleh);
ctx.restore();
show_result()
}
update();
render();
}
function gameStateGameOver(){
if (gameOver != true){
bouncecount=0;
ctx.fillStyle = '#000000';
ctx.fillRect(0,0,500,400);
ctx.fillStyle = '#ffffff';
ctx.font = '20px _sans';
ctx.textBaseline = 'top';
ctx.fillText ("Game over", 200,150);
ctx.fillText ("Press Space to Restart", 160,200);
ctx.fillText ("You completed " + difficulty + " levels", 160,240);
difficulty=0;
gameOver = true;
}else{
if (keyPressList[32] == true){
switchGameState(GAME_STATE_TITLE);
gameOver = false;
}
}
}
function runGame(){
currentGameStateFunction();
}
// Key handler
document.onkeydown = function(e){
e= e?e:window.event;
keyPressList[e.keyCode] = true;
}
document.onkeyup = function(e){
e= e?e:window.event;
keyPressList[e.keyCode] = false;
}
function onMouseMove(evt) {
// Event data passes to this function
mouseX = evt.clientX-canvas.offsetLeft - paddlew/2;
// Assign the relative position of the mouse in the canvas to mouseX
mouseY = evt.clientY-canvas.offsetTop;
//Do the same for mouseY
document.title="("+mouseX+","+mouseY+")";
//Put the mouse X and Y in the title for info
paddlex = mouseX;
// Position the paddle
}
canvas.addEventListener("mousemove",onMouseMove, false);
//Application start
switchGameState(GAME_STATE_TITLE);
const FRAME_RATE = 40;
var intervalTime = 1000/FRAME_RATE;
setInterval(runGame, intervalTime);
function show_result(){
ctx.fillText ("There are " + brickcount + " bricks", 160,200);
ctx.fillText ("Paddle bounces are " + bouncecount , 160,220);
}
}
With proper indenting, your code looks like this:
bricks = new Array(NROWS);
for (i=0; i < NROWS; i++) {
bricks[i] = new Array(NCOLS);
for (j=0; j < NCOLS; j++) {
bricks[i][j] = 1;
}
bricks[0][10]=0;
bricks[7][16]=0;
In other words, you're attempting to access bricks[7] in the very first iteration when only bricks[0] has been created. Properly close the first for loop with a } before running your list of overrides.
You may have played Snake, a game where you have to eat food to grow and you fail if you collide with the snake's body or certain obstacles. The first part was easy, but the latter seems impossible to achieve.
I have tried to make a for loop check if the last element of my snake array is colliding with its other parts. My condition was like this: if the x position of the last item in my array is bigger than any of the array items' x position, and smaller than their x position plus their width, and so on. That didn't work.
Here's my code :
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<canvas id="myCanvas" width="200px" height="200px" style="border:1px solid black"/>
<script>
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var yPos = 20;
var width = 15;
var variable = 1;
var currentDir = 1;
//var xPos = (width+5)*variable;
var xPos = 20;
var myArr = [{myX:xPos,myY:yPos},{myX:xPos,myY:yPos},{myX:xPos,myY:yPos}];
var downPressed = false;
var upPressed = false;
var leftPressed = false;
var rightPressed = false;
var first = [0,20,40,60,80,100,120,140,160,180];
var firstX = Math.floor(Math.random()*10);
var firstY = Math.floor(Math.random()*10);
var okayed = first[firstX];
var notOkayed = first[firstY];
var maths = myArr[myArr.length-1];
function drawFood() {
ctx.beginPath();
ctx.rect(okayed,notOkayed,15,15);
ctx.fillStyle = "red";
ctx.fill();
ctx.closePath();
}
function drawRectangle() {
ctx.clearRect(0,0,200,200);
drawFood();
for(var i = 0;i<myArr.length;i++) {
ctx.beginPath();
ctx.rect(myArr[i].myX,myArr[i].myY,width,15);
ctx.fillStyle = "blue";
ctx.fill();
ctx.closePath();
}
requestAnimationFrame(drawRectangle);
}
setInterval("calledin()",100);
function calledin() {
var secondX = Math.floor(Math.random()*10);
var secondY = Math.floor(Math.random()*10);
var newobj = {myX:myArr[myArr.length-1].myX+20,myY:myArr[myArr.length-1].myY};
var newobjTwo = {myX:myArr[myArr.length-1].myX,myY:myArr[myArr.length-1].myY+20};
var newobjLeft = {myX:myArr[myArr.length-1].myX-20,myY:myArr[myArr.length-1].myY};
var newobjUp = {myX:myArr[myArr.length-1].myX,myY:myArr[myArr.length-1].myY-20};
var okayNewObj = {myX:myArr[1].myX - 20,myY:myArr[1].myY};
if(myArr[myArr.length-1].myX > 180 || myArr[myArr.length-1].myX < 0 || myArr[myArr.length-1].myY > 180 || myArr[myArr.length-1].myY < 0)
{alert("Game Over");window.location.reload();}
if(myArr[myArr.length-1].myX > okayed-5 && myArr[myArr.length-1].myX < okayed+20 && myArr[myArr.length-1].myY < notOkayed+20 &&
myArr[myArr.length-1].myY > notOkayed-5) {
okayed = first[secondX];
notOkayed = first[secondY];
myArr.unshift(okayNewObj);
}
if(currentDir == 1) {
myArr.push(newobj);
myArr.shift();}
if(currentDir == 2) {
myArr.push(newobjTwo);
myArr.shift();
}
if(currentDir == 4) {
myArr.push(newobjLeft);
myArr.shift();
}
if(currentDir == 3) {
myArr.push(newobjUp);
myArr.shift();
}
for(var i = 0;i<myArr.length-2;i++) {
if(myArr[myArr.length-1].myX > myArr[i].myX &&
myArr[myArr.length-1].myX < myArr[i].myX + 15 && myArr[myArr.length-1].myY > myArr[i].myY && myArr[myArr.length-1].myY > myArr[i].myY + 15)
{alert("Game over");window.location.reload();}
}
}
function downed(e) {
if(e.keyCode==40) {if(currentDir != 3) {currentDir = 2;}}
if(e.keyCode==38) {if(currentDir != 2) {currentDir = 3;}}
if(e.keyCode==39) {if(currentDir != 4) {currentDir = 1;}}
if(e.keyCode==37) {if(currentDir != 1) {currentDir = 4;}}
}
function upped(e) {
if(e.keyCode == 40) {downPressed = false;}
}
document.addEventListener("keydown",downed,false);
document.addEventListener("keyup",upped,false);
drawRectangle();
</script>
</body>
</html>
Suppose the snake is represented by an array called snake in which the head is at index snake.length - 1. We have to compare the position of the head against the positions of the body segments at indices 0 through snake.length - 2.
The following code sets okay to false if the snake head has collided with a body segment. Otherwise, okay remains true.
var head = snake[snake.length - 1],
x = head.x,
y = head.y,
okay = true;
for (var i = snake.length - 2; i >= 0; --i) {
if (snake[i].x == x && snake[i].y == y) {
okay = false;
break;
}
}
Below is a snippet in which I have modified your code to clarify the game logic and to simplify many of the calculations.
Instead of working directly with canvas coordinates, I represent each position with the column index x and row index y of a virtual grid cell. This lets us calculate the neighboring grid positions by adding 1 or -1 to x or y. When it comes time to paint the canvas, we multiply the virtual coordinates by the cell size.
I have replaced most of your literal values with variables. For example, instead of setting the canvas dimensions to 200 by 200, we can do this:
canvas.width = numCols * cellSize;
canvas.height = numRows * cellSize;
This lets us change numCols and numRows in one place to resize the whole game grid. All the calculations work out because they evaluate variables instead of using literals.
I altered the key-event handling to recognize the key codes for the W-A-S-D keys in addition to the arrow keys. When the game is embedded in a long web page, as it is here, you'll probably want to use the W-A-S-D keys so that the page doesn't scroll up and down while you're playing.
var canvas,
ctx,
currentDir,
startX = 1,
startY = 1,
startSnakeLength = 3,
snake,
cellSize = 18,
cellGap = 1,
foodColor = '#a2302a',
snakeBodyColor = '#2255a2',
snakeHeadColor = '#0f266b',
numRows = 10,
numCols = 10,
canvasWidth = numCols * cellSize,
canvasHeight = numRows * cellSize;
var food = {};
function placeFood() {
// Find a random location that isn't occupied by the snake.
var okay = false;
while (!okay) {
food.x = Math.floor(Math.random() * numCols);
food.y = Math.floor(Math.random() * numRows);
okay = true;
for (var i = 0; i < snake.length; ++i) {
if (snake[i].x == food.x && snake[i].y == food.y) {
okay = false;
break;
}
}
}
}
function paintCell(x, y, color) {
ctx.fillStyle = color;
ctx.fillRect(x * cellSize + cellGap,
y * cellSize + cellGap,
cellSize - cellGap,
cellSize - cellGap);
}
function paintCanvas() {
ctx.clearRect(0, 0, canvasWidth, canvasHeight);
paintCell(food.x, food.y, foodColor);
var head = snake[snake.length - 1];
paintCell(head.x, head.y, snakeHeadColor);
for (var i = snake.length - 2; i >= 0; --i) {
paintCell(snake[i].x, snake[i].y, snakeBodyColor);
}
}
function updateGame() {
var head = snake[snake.length - 1],
x = head.x,
y = head.y;
// Move the snake.
var tail = snake.shift();
switch (currentDir) {
case 'up':
snake.push(head = { x: x, y: y - 1 });
break;
case 'right':
snake.push(head = { x: x + 1, y: y });
break;
case 'down':
snake.push(head = { x: x, y: y + 1 });
break;
case 'left':
snake.push(head = { x: x - 1, y: y });
break;
}
paintCanvas();
x = head.x;
y = head.y;
// Check for wall collision.
if (x < 0 || x >= numCols || y < 0 || y >= numRows) {
stopGame('wall collision');
return;
}
// Check for snake head colliding with snake body.
for (var i = snake.length - 2; i >= 0; --i) {
if (snake[i].x == x && snake[i].y == y) {
stopGame('self-collision');
return;
}
}
// Check for food.
if (x == food.x && y == food.y) {
placeFood();
snake.unshift(tail);
setMessage(snake.length + ' segments');
}
}
var dirToKeyCode = { // Codes for arrow keys and W-A-S-D.
up: [38, 87],
right: [39, 68],
down: [40, 83],
left: [37, 65]
},
keyCodeToDir = {}; // Fill this from dirToKeyCode on page load.
function keyDownHandler(e) {
var keyCode = e.keyCode;
if (keyCode in keyCodeToDir) {
currentDir = keyCodeToDir[keyCode];
}
}
function setMessage(s) {
document.getElementById('messageBox').innerHTML = s;
}
function startGame() {
currentDir = 'right';
snake = new Array(startSnakeLength);
snake[snake.length - 1] = { x: startX, y: startY };
for (var i = snake.length - 2; i >= 0; --i) {
snake[i] = { x: snake[i + 1].x, y: snake[i + 1].y + 1 };
}
placeFood();
paintCanvas();
setMessage('');
gameInterval = setInterval(updateGame, 200);
startGameButton.disabled = true;
}
function stopGame(message) {
setMessage(message + '<br> ended with ' + snake.length + ' segments');
clearInterval(gameInterval);
startGameButton.disabled = false;
}
var gameInterval,
startGameButton;
window.onload = function () {
canvas = document.getElementById('gameCanvas'),
ctx = canvas.getContext('2d');
canvas.width = numCols * cellSize;
canvas.height = numRows * cellSize;
Object.keys(dirToKeyCode).forEach(function (dir) {
dirToKeyCode[dir].forEach(function (keyCode) {
keyCodeToDir[keyCode] = dir;
})
});
document.addEventListener("keydown", keyDownHandler, false);
startGameButton = document.getElementById('startGameButton');
startGameButton.onclick = startGame;
}
body {
font-family: sans-serif;
}
#gameCanvas {
border: 1px solid #000;
float: left;
margin-right: 15px;
}
#startGameButton, #messageBox {
font-size: 16px;
margin-top: 15px;
}
#messageBox {
line-height: 24px;
}
<canvas id="gameCanvas"></canvas>
<button id="startGameButton">Start game</button>
<div id="messageBox"></div>