Develop Reference

Change color of Paticle(circle) when collision detected in canvas

// Initial Setup
const canvas = document.querySelector('canvas');
const c = canvas.getContext('2d');
// Canvas size
canvas.width = innerWidth;
canvas.height = innerHeight;
//Color
const colors = [
{r: 51, g: 99, b: 252}
//{r: 77, g: 57, b: 206},
// {r: 0, g: 189, b: 255},
];
// Utility Functions
function randomIntFromRange(min, max) {
return Math.floor(Math.random() * (max - min + 1) + min);
}
function randomColor(colors) {
return colors[Math.floor(Math.random() * colors.length)];
}
function distance(x1, y1, x2, y2) {
const xDist = x2 - x1;
const yDist = y2 - y1;
return Math.sqrt(Math.pow(xDist, 2) + Math.pow(yDist, 2));
}
function rotateVelocities(velocity, theta) {
const rotatedVelocity = {
x: velocity.x * Math.cos(theta) - velocity.y * Math.sin(theta),
y: velocity.x * Math.sin(theta) + velocity.y * Math.cos(theta)
};
return rotatedVelocity;
}
// Objects
function Particle(x, y, radius, rgb) {
this.x = x;
this.y = y;
this.velocity = {
x: (Math.random() - 0.5) * 3,
y: (Math.random() - 0.5) * 3
};
this.radius = radius;
this.mass = 1;
this.opacity = 0;
this.r = rgb.r;
this.g = rgb.g;
this.b = rgb.b;
this.update = particles => {
this.draw();
for (let i = 0; i < particles.length; i++) {
const otherParticle = particles[i];
if (this.x === otherParticle.x) continue;
if (distance(this.x, this.y, otherParticle.x, otherParticle.y) - this.radius * 2 < 0) {
const res = {
x: this.velocity.x - otherParticle.velocity.x,
y: this.velocity.y - otherParticle.velocity.y
};
if (res.x * (otherParticle.x - this.x) + res.y * (otherParticle.y - this.y) >= 0) {
const m1 = this.mass;
const m2 = otherParticle.mass;
const theta = -Math.atan2(otherParticle.y - this.y, otherParticle.x - this.x);
const rotatedVelocity1 = rotateVelocities(this.velocity, theta);
const rotatedVelocity2 = rotateVelocities(otherParticle.velocity, theta);
const swapVelocity1 = { x: rotatedVelocity1.x * (m1 - m2) / (m1 + m2) + rotatedVelocity2.x * 2 * m2 / (m1 + m2), y: rotatedVelocity1.y };
const swapVelocity2 = { x: rotatedVelocity2.x * (m1 - m2) / (m1 + m2) + rotatedVelocity1.x * 2 * m2 / (m1 + m2), y: rotatedVelocity2.y };
const u1 = rotateVelocities(swapVelocity1, -theta);
const u2 = rotateVelocities(swapVelocity2, -theta);
this.velocity.x = u1.x;
this.velocity.y = u1.y;
otherParticle.velocity.x = u2.x;
otherParticle.velocity.y = u2.y;
}
}
if (distance(this.x, this.y, otherParticle.x, otherParticle.y) - this.radius * 2 < 0 ) {
this.opacity = 0.1;
}
}
if (this.x + this.radius >= canvas.width || this.x - this.radius <= 0)
this.velocity.x = -this.velocity.x;
if (this.y + this.radius >= canvas.height || this.y - this.radius <= 0)
this.velocity.y = -this.velocity.y;
this.x += this.velocity.x;
this.y += this.velocity.y;
};
this.draw = () => {
c.beginPath();
c.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
c.strokeStyle = `rgba(${this.r}, ${this.g}, ${this.b}, 1)`;
c.stroke();
c.fillStyle = `rgba(${this.r}, ${this.g}, ${this.b}, ${this.opacity}`;
c.fill();
c.closePath();
};
}
// Implementation
let particles;
function init() {
particles = [];
let radius = 80
for (let i = 0; i < 10; i++) {
let x = randomIntFromRange(radius, innerWidth - radius);
let y = randomIntFromRange(radius, innerHeight - radius);
if (particles.length >= 1) {
for (let j = 0; j < particles.length; j++) {
if (distance(x, y, particles[j].x, particles[j].y) - radius * 2 < 0) {
x = randomIntFromRange(radius, innerWidth - radius);
y = randomIntFromRange(radius, innerHeight - radius);
j = -1;
continue;
}
}
}
particles.push(new Particle(x, y, radius, randomColor(colors)));
}
}
//I would like to initiate one circle out of all as red and whenever the red circle collide with other circle, other circle got red and at last all circle become red. but when two white circle collide it should not become red. basically one infected circle making other circle infected by touching.

I need to make this canvas transparent but none of the solutions are working

I have tried all the jQuery tricks as well as the CSS tricks, but none of them work.. I don't really know anything about <canvas> but I've been trying to solve this for a day now.. can anybody help?
I am trying not mess up the code and just make the black background transparent so that I could use this canvas over a carousal..
// helper functions
const PI2 = Math.PI * 2
const random = (min, max) => Math.random() * (max - min + 1) + min | 0
const timestamp = _ => new Date().getTime()
// container
class Birthday {
constructor() {
this.resize()
// create a lovely place to store the firework
this.fireworks = []
this.counter = 0
}
resize() {
this.width = canvas.width = window.innerWidth
let center = this.width / 2 | 0
this.spawnA = center - center / 4 | 0
this.spawnB = center + center / 4 | 0
this.height = canvas.height = window.innerHeight
this.spawnC = this.height * .1
this.spawnD = this.height * .5
}
onClick(evt) {
let x = evt.clientX || evt.touches && evt.touches[0].pageX
let y = evt.clientY || evt.touches && evt.touches[0].pageY
let count = random(3, 5)
for (let i = 0; i < count; i++) this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
x,
y,
random(0, 260),
random(30, 110)))
this.counter = -1
}
update(delta) {
ctx.globalCompositeOperation = 'hard-light'
ctx.fillStyle = `rgba(20,20,20,${ 7 * delta })`
ctx.fillRect(0, 0, this.width, this.height)
ctx.globalCompositeOperation = 'lighter'
for (let firework of this.fireworks) firework.update(delta)
// if enough time passed... create new new firework
this.counter += delta * 3 // each second
if (this.counter >= 1) {
this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
random(0, this.width),
random(this.spawnC, this.spawnD),
random(0, 360),
random(30, 110)))
this.counter = 0
}
// remove the dead fireworks
if (this.fireworks.length > 1000) this.fireworks = this.fireworks.filter(firework => !firework.dead)
}
}
class Firework {
constructor(x, y, targetX, targetY, shade, offsprings) {
this.dead = false
this.offsprings = offsprings
this.x = x
this.y = y
this.targetX = targetX
this.targetY = targetY
this.shade = shade
this.history = []
}
update(delta) {
if (this.dead) return
let xDiff = this.targetX - this.x
let yDiff = this.targetY - this.y
if (Math.abs(xDiff) > 3 || Math.abs(yDiff) > 3) { // is still moving
this.x += xDiff * 2 * delta
this.y += yDiff * 2 * delta
this.history.push({
x: this.x,
y: this.y
})
if (this.history.length > 20) this.history.shift()
} else {
if (this.offsprings && !this.madeChilds) {
let babies = this.offsprings / 2
for (let i = 0; i < babies; i++) {
let targetX = this.x + this.offsprings * Math.cos(PI2 * i / babies) | 0
let targetY = this.y + this.offsprings * Math.sin(PI2 * i / babies) | 0
birthday.fireworks.push(new Firework(this.x, this.y, targetX, targetY, this.shade, 0))
}
}
this.madeChilds = true
this.history.shift()
}
if (this.history.length === 0) this.dead = true
else if (this.offsprings) {
for (let i = 0; this.history.length > i; i++) {
let point = this.history[i]
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,' + i + '%)'
ctx.arc(point.x, point.y, 1, 0, PI2, false)
ctx.fill()
}
} else {
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,50%)'
ctx.arc(this.x, this.y, 1, 0, PI2, false)
ctx.fill()
}
}
}
let canvas = document.getElementById('birthday')
let ctx = canvas.getContext('2d')
let then = timestamp()
let birthday = new Birthday
window.onresize = () => birthday.resize()
document.onclick = evt => birthday.onClick(evt)
document.ontouchstart = evt => birthday.onClick(evt)
;
(function loop() {
requestAnimationFrame(loop)
let now = timestamp()
let delta = now - then
then = now
birthday.update(delta / 1000)
})()
<canvas id="birthday"></canvas>

All you need to do is replace fillRect with clearRect in the update method of the Birthday class like this:
ctx.clearRect(0, 0, this.width, this.height)
You may need to make further adjustments to the color of the firework trail though, since it seems like it was supposed to match the background color.
If your canvas still isn't transparent, check your css to ensure that you're not setting the background color that way.
const PI2 = Math.PI * 2
const random = (min, max) => Math.random() * (max - min + 1) + min | 0
const timestamp = _ => new Date().getTime()
// container
class Birthday {
constructor() {
this.resize()
// create a lovely place to store the firework
this.fireworks = []
this.counter = 0
}
resize() {
this.width = canvas.width = window.innerWidth
let center = this.width / 2 | 0
this.spawnA = center - center / 4 | 0
this.spawnB = center + center / 4 | 0
this.height = canvas.height = window.innerHeight
this.spawnC = this.height * .1
this.spawnD = this.height * .5
}
onClick(evt) {
let x = evt.clientX || evt.touches && evt.touches[0].pageX
let y = evt.clientY || evt.touches && evt.touches[0].pageY
let count = random(3, 5)
for (let i = 0; i < count; i++) this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
x,
y,
random(0, 260),
random(30, 110)))
this.counter = -1
}
update(delta) {
ctx.globalCompositeOperation = 'hard-light'
ctx.fillStyle = `rgba(20,20,20,${ 7 * delta })`
ctx.clearRect(0, 0, this.width, this.height)
ctx.globalCompositeOperation = 'lighter'
for (let firework of this.fireworks) firework.update(delta)
// if enough time passed... create new new firework
this.counter += delta * 3 // each second
if (this.counter >= 1) {
this.fireworks.push(new Firework(
random(this.spawnA, this.spawnB),
this.height,
random(0, this.width),
random(this.spawnC, this.spawnD),
random(0, 360),
random(30, 110)))
this.counter = 0
}
// remove the dead fireworks
if (this.fireworks.length > 1000) this.fireworks = this.fireworks.filter(firework => !firework.dead)
}
}
class Firework {
constructor(x, y, targetX, targetY, shade, offsprings) {
this.dead = false
this.offsprings = offsprings
this.x = x
this.y = y
this.targetX = targetX
this.targetY = targetY
this.shade = shade
this.history = []
}
update(delta) {
if (this.dead) return
let xDiff = this.targetX - this.x
let yDiff = this.targetY - this.y
if (Math.abs(xDiff) > 3 || Math.abs(yDiff) > 3) { // is still moving
this.x += xDiff * 2 * delta
this.y += yDiff * 2 * delta
this.history.push({
x: this.x,
y: this.y
})
if (this.history.length > 20) this.history.shift()
} else {
if (this.offsprings && !this.madeChilds) {
let babies = this.offsprings / 2
for (let i = 0; i < babies; i++) {
let targetX = this.x + this.offsprings * Math.cos(PI2 * i / babies) | 0
let targetY = this.y + this.offsprings * Math.sin(PI2 * i / babies) | 0
birthday.fireworks.push(new Firework(this.x, this.y, targetX, targetY, this.shade, 0))
}
}
this.madeChilds = true
this.history.shift()
}
if (this.history.length === 0) this.dead = true
else if (this.offsprings) {
for (let i = 0; this.history.length > i; i++) {
let point = this.history[i]
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,' + i + '%)'
ctx.arc(point.x, point.y, 1, 0, PI2, false)
ctx.fill()
}
} else {
ctx.beginPath()
ctx.fillStyle = 'hsl(' + this.shade + ',100%,50%)'
ctx.arc(this.x, this.y, 1, 0, PI2, false)
ctx.fill()
}
}
}
let canvas = document.getElementById('birthday')
let ctx = canvas.getContext('2d')
let then = timestamp()
let birthday = new Birthday
window.onresize = () => birthday.resize()
document.onclick = evt => birthday.onClick(evt)
document.ontouchstart = evt => birthday.onClick(evt)
;
(function loop() {
requestAnimationFrame(loop)
let now = timestamp()
let delta = now - then
then = now
birthday.update(delta / 1000)
})()
div {
height : 100vh;
width : 100vw;
display : flex;
flex-direction : center;
align-items : center;
justify-content : center;
}
canvas {
position : absolute;
top : 0;
left : 0;
}
<div>Content Underneath</div>
<canvas id="birthday"></canvas>

javascript code limited by text position in the html page

i'm trying to use this Fireworks javascript. But when i write some text in the middle of the HTML page, the fireworks will not go over it and is limited by the text position...how can i override this and keep the fireworks go up to the top of the page ?
i tryed to fix the SCREEN_WIDTH and SCREEN_HEIGHT position but it doesn't work...
var SCREEN_WIDTH = window.innerWidth,
SCREEN_HEIGHT = window.innerHeight,
mousePos = {
x: 400,
y: 300
},
// create canvas
canvas = document.createElement('canvas'),
context = canvas.getContext('2d'),
particles = [],
rockets = [],
MAX_PARTICLES = 400,
colorCode = 0;
// init
$(document).ready(function() {
document.body.appendChild(canvas);
canvas.width = SCREEN_WIDTH;
canvas.height = SCREEN_HEIGHT;
setInterval(launch, 800);
setInterval(loop, 1000 / 50);
});
// update mouse position
$(document).mousemove(function(e) {
e.preventDefault();
mousePos = {
x: e.clientX,
y: e.clientY
};
});
// launch more rockets!!!
$(document).mousedown(function(e) {
for (var i = 0; i < 5; i++) {
launchFrom(Math.random() * SCREEN_WIDTH * 2 / 3 + SCREEN_WIDTH / 6);
}
});
function launch() {
launchFrom(mousePos.x);
}
function launchFrom(x) {
if (rockets.length < 10) {
var rocket = new Rocket(x);
rocket.explosionColor = Math.floor(Math.random() * 360 / 10) * 10;
rocket.vel.y = Math.random() * -3 - 4;
rocket.vel.x = Math.random() * 6 - 3;
rocket.size = 8;
rocket.shrink = 0.999;
rocket.gravity = 0.01;
rockets.push(rocket);
}
}
function loop() {
// update screen size
if (SCREEN_WIDTH != window.innerWidth) {
canvas.width = SCREEN_WIDTH = window.innerWidth;
}
if (SCREEN_HEIGHT != window.innerHeight) {
canvas.height = SCREEN_HEIGHT = window.innerHeight;
}
// clear canvas
context.fillStyle = "rgba(0, 0, 0, 0.05)";
context.fillRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
var existingRockets = [];
for (var i = 0; i < rockets.length; i++) {
// update and render
rockets[i].update();
rockets[i].render(context);
// calculate distance with Pythagoras
var distance = Math.sqrt(Math.pow(mousePos.x - rockets[i].pos.x, 2) + Math.pow(mousePos.y - rockets[i].pos.y, 2));
// random chance of 1% if rockets is above the middle
var randomChance = rockets[i].pos.y < (SCREEN_HEIGHT * 2 / 3) ? (Math.random() * 100 <= 1) : false;
/* Explosion rules
- 80% of screen
- going down
- close to the mouse
- 1% chance of random explosion
*/
if (rockets[i].pos.y < SCREEN_HEIGHT / 5 || rockets[i].vel.y >= 0 || distance < 50 || randomChance) {
rockets[i].explode();
} else {
existingRockets.push(rockets[i]);
}
}
rockets = existingRockets;
var existingParticles = [];
for (var i = 0; i < particles.length; i++) {
particles[i].update();
// render and save particles that can be rendered
if (particles[i].exists()) {
particles[i].render(context);
existingParticles.push(particles[i]);
}
}
// update array with existing particles - old particles should be garbage collected
particles = existingParticles;
while (particles.length > MAX_PARTICLES) {
particles.shift();
}
}
function Particle(pos) {
this.pos = {
x: pos ? pos.x : 0,
y: pos ? pos.y : 0
};
this.vel = {
x: 0,
y: 0
};
this.shrink = .97;
this.size = 2;
this.resistance = 1;
this.gravity = 0;
this.flick = false;
this.alpha = 1;
this.fade = 0;
this.color = 0;
}
Particle.prototype.update = function() {
// apply resistance
this.vel.x *= this.resistance;
this.vel.y *= this.resistance;
// gravity down
this.vel.y += this.gravity;
// update position based on speed
this.pos.x += this.vel.x;
this.pos.y += this.vel.y;
// shrink
this.size *= this.shrink;
// fade out
this.alpha -= this.fade;
};
Particle.prototype.render = function(c) {
if (!this.exists()) {
return;
}
c.save();
c.globalCompositeOperation = 'lighter';
var x = this.pos.x,
y = this.pos.y,
r = this.size / 2;
var gradient = c.createRadialGradient(x, y, 0.1, x, y, r);
gradient.addColorStop(0.1, "rgba(255,255,255," + this.alpha + ")");
gradient.addColorStop(0.8, "hsla(" + this.color + ", 100%, 50%, " + this.alpha + ")");
gradient.addColorStop(1, "hsla(" + this.color + ", 100%, 50%, 0.1)");
c.fillStyle = gradient;
c.beginPath();
c.arc(this.pos.x, this.pos.y, this.flick ? Math.random() * this.size : this.size, 0, Math.PI * 2, true);
c.closePath();
c.fill();
c.restore();
};
Particle.prototype.exists = function() {
return this.alpha >= 0.1 && this.size >= 1;
};
function Rocket(x) {
Particle.apply(this, [{
x: x,
y: SCREEN_HEIGHT}]);
this.explosionColor = 0;
}
Rocket.prototype = new Particle();
Rocket.prototype.constructor = Rocket;
Rocket.prototype.explode = function() {
var count = Math.random() * 10 + 80;
for (var i = 0; i < count; i++) {
var particle = new Particle(this.pos);
var angle = Math.random() * Math.PI * 2;
// emulate 3D effect by using cosine and put more particles in the middle
var speed = Math.cos(Math.random() * Math.PI / 2) * 15;
particle.vel.x = Math.cos(angle) * speed;
particle.vel.y = Math.sin(angle) * speed;
particle.size = 10;
particle.gravity = 0.2;
particle.resistance = 0.92;
particle.shrink = Math.random() * 0.05 + 0.93;
particle.flick = true;
particle.color = this.explosionColor;
particles.push(particle);
}
};
Rocket.prototype.render = function(c) {
if (!this.exists()) {
return;
}
c.save();
c.globalCompositeOperation = 'lighter';
var x = this.pos.x,
y = this.pos.y,
r = this.size / 2;
var gradient = c.createRadialGradient(x, y, 0.1, x, y, r);
gradient.addColorStop(0.1, "rgba(255, 255, 255 ," + this.alpha + ")");
gradient.addColorStop(1, "rgba(0, 0, 0, " + this.alpha + ")");
c.fillStyle = gradient;
c.beginPath();
c.arc(this.pos.x, this.pos.y, this.flick ? Math.random() * this.size / 2 + this.size / 2 : this.size, 0, Math.PI * 2, true);
c.closePath();
c.fill();
c.restore();
};
body {
background-color: #000000;
margin: 0px;
overflow: hidden;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Fireworks!</title>
</head>
<body/>
</html>

The problem is the canvas used by the script is positioned relative by default. To make it always visible completely on screen we have to make it fixed and set the top and left CSS values to 0.
Now because its fixed the canvas renders on top of everything. To get it in the background set z-index to -1.
All additions together:
canvas.style.position="fixed";
canvas.style.top="0";
canvas.style.left="0";
canvas.style.zIndex="-1";
Complete Source:
var SCREEN_WIDTH = window.innerWidth,
SCREEN_HEIGHT = window.innerHeight,
mousePos = {
x: 400,
y: 300
},
// create canvas
canvas = document.createElement('canvas'),
context = canvas.getContext('2d'),
particles = [],
rockets = [],
MAX_PARTICLES = 400,
colorCode = 0;
// init
$(document).ready(function() {
document.body.appendChild(canvas);
canvas.width = SCREEN_WIDTH;
canvas.height = SCREEN_HEIGHT;
canvas.style.position = "fixed";
canvas.style.top = "0";
canvas.style.left = "0";
canvas.style.zIndex = "-1";
setInterval(launch, 800);
setInterval(loop, 1000 / 50);
});
// update mouse position
$(document).mousemove(function(e) {
e.preventDefault();
mousePos = {
x: e.clientX,
y: e.clientY
};
});
// launch more rockets!!!
$(document).mousedown(function(e) {
for (var i = 0; i < 5; i++) {
launchFrom(Math.random() * SCREEN_WIDTH * 2 / 3 + SCREEN_WIDTH / 6);
}
});
function launch() {
launchFrom(mousePos.x);
}
function launchFrom(x) {
if (rockets.length < 10) {
var rocket = new Rocket(x);
rocket.explosionColor = Math.floor(Math.random() * 360 / 10) * 10;
rocket.vel.y = Math.random() * -3 - 4;
rocket.vel.x = Math.random() * 6 - 3;
rocket.size = 8;
rocket.shrink = 0.999;
rocket.gravity = 0.01;
rockets.push(rocket);
}
}
function loop() {
// update screen size
if (SCREEN_WIDTH != window.innerWidth) {
canvas.width = SCREEN_WIDTH = window.innerWidth;
}
if (SCREEN_HEIGHT != window.innerHeight) {
canvas.height = SCREEN_HEIGHT = window.innerHeight;
}
// clear canvas
context.fillStyle = "rgba(0, 0, 0, 0.05)";
context.fillRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
var existingRockets = [];
for (var i = 0; i < rockets.length; i++) {
// update and render
rockets[i].update();
rockets[i].render(context);
// calculate distance with Pythagoras
var distance = Math.sqrt(Math.pow(mousePos.x - rockets[i].pos.x, 2) + Math.pow(mousePos.y - rockets[i].pos.y, 2));
// random chance of 1% if rockets is above the middle
var randomChance = rockets[i].pos.y < (SCREEN_HEIGHT * 2 / 3) ? (Math.random() * 100 <= 1) : false;
/* Explosion rules
- 80% of screen
- going down
- close to the mouse
- 1% chance of random explosion
*/
if (rockets[i].pos.y < SCREEN_HEIGHT / 5 || rockets[i].vel.y >= 0 || distance < 50 || randomChance) {
rockets[i].explode();
} else {
existingRockets.push(rockets[i]);
}
}
rockets = existingRockets;
var existingParticles = [];
for (var i = 0; i < particles.length; i++) {
particles[i].update();
// render and save particles that can be rendered
if (particles[i].exists()) {
particles[i].render(context);
existingParticles.push(particles[i]);
}
}
// update array with existing particles - old particles should be garbage collected
particles = existingParticles;
while (particles.length > MAX_PARTICLES) {
particles.shift();
}
}
function Particle(pos) {
this.pos = {
x: pos ? pos.x : 0,
y: pos ? pos.y : 0
};
this.vel = {
x: 0,
y: 0
};
this.shrink = .97;
this.size = 2;
this.resistance = 1;
this.gravity = 0;
this.flick = false;
this.alpha = 1;
this.fade = 0;
this.color = 0;
}
Particle.prototype.update = function() {
// apply resistance
this.vel.x *= this.resistance;
this.vel.y *= this.resistance;
// gravity down
this.vel.y += this.gravity;
// update position based on speed
this.pos.x += this.vel.x;
this.pos.y += this.vel.y;
// shrink
this.size *= this.shrink;
// fade out
this.alpha -= this.fade;
};
Particle.prototype.render = function(c) {
if (!this.exists()) {
return;
}
c.save();
c.globalCompositeOperation = 'lighter';
var x = this.pos.x,
y = this.pos.y,
r = this.size / 2;
var gradient = c.createRadialGradient(x, y, 0.1, x, y, r);
gradient.addColorStop(0.1, "rgba(255,255,255," + this.alpha + ")");
gradient.addColorStop(0.8, "hsla(" + this.color + ", 100%, 50%, " + this.alpha + ")");
gradient.addColorStop(1, "hsla(" + this.color + ", 100%, 50%, 0.1)");
c.fillStyle = gradient;
c.beginPath();
c.arc(this.pos.x, this.pos.y, this.flick ? Math.random() * this.size : this.size, 0, Math.PI * 2, true);
c.closePath();
c.fill();
c.restore();
};
Particle.prototype.exists = function() {
return this.alpha >= 0.1 && this.size >= 1;
};
function Rocket(x) {
Particle.apply(this, [{
x: x,
y: SCREEN_HEIGHT
}]);
this.explosionColor = 0;
}
Rocket.prototype = new Particle();
Rocket.prototype.constructor = Rocket;
Rocket.prototype.explode = function() {
var count = Math.random() * 10 + 80;
for (var i = 0; i < count; i++) {
var particle = new Particle(this.pos);
var angle = Math.random() * Math.PI * 2;
// emulate 3D effect by using cosine and put more particles in the middle
var speed = Math.cos(Math.random() * Math.PI / 2) * 15;
particle.vel.x = Math.cos(angle) * speed;
particle.vel.y = Math.sin(angle) * speed;
particle.size = 10;
particle.gravity = 0.2;
particle.resistance = 0.92;
particle.shrink = Math.random() * 0.05 + 0.93;
particle.flick = true;
particle.color = this.explosionColor;
particles.push(particle);
}
};
Rocket.prototype.render = function(c) {
if (!this.exists()) {
return;
}
c.save();
c.globalCompositeOperation = 'lighter';
var x = this.pos.x,
y = this.pos.y,
r = this.size / 2;
var gradient = c.createRadialGradient(x, y, 0.1, x, y, r);
gradient.addColorStop(0.1, "rgba(255, 255, 255 ," + this.alpha + ")");
gradient.addColorStop(1, "rgba(0, 0, 0, " + this.alpha + ")");
c.fillStyle = gradient;
c.beginPath();
c.arc(this.pos.x, this.pos.y, this.flick ? Math.random() * this.size / 2 + this.size / 2 : this.size, 0, Math.PI * 2, true);
c.closePath();
c.fill();
c.restore();
};
body {
background-color: #000000;
margin: 0px;
overflow: hidden;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Fireworks!</title>
</head>
<body>
<p>
test
</p>
<br />
<p>
test2
</p>
</body>
</html>

Clickable Canvas Button with Link

I have the following canvas. I want it so that when the user clicks the canvas, I will go to google.com, and I want to keep the button element. This is my code:
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
a.style.width = '200px';
a.style.height = '50px';
area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = .01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - .05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if(this.r <= .05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0,0,w,h);
for(var i = 0; i < particles.length; i++) {
if(particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if(particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for(var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max)?max:1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
#canvas{
width: 200;
height: 50;
}
<div class="wrapper">
<a href="index.html">
<button align=center onclick="handleClick()">
<canvas width="200" height="50" id="canvas" align=center></canvas>
<span class="text">SUBMIT</span>
</button>
</a>
</div>
Although, I only see the button, and no the canvas. How can I fix this?

You got a lot of errors actually buddy (variable declaration is the biggest problem) but by following the errors will give you a way to fix it, I don't know if this is the fix you want.
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d');
a.style.width = '200px';
a.style.height = '50px';
var w, h;
var area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = 0.01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - 0.05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if (this.r <= 0.05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0, 0, w, h);
for (var i = 0; i < particles.length; i++) {
if (particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if (particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for (var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max) ? max : 1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
#canvas {
width: 200px;
height: 50px;
}
<div class="wrapper">
<a href="index.html">
<button align=center onclick="handleClick()">
<canvas width="200" height="50" id="canvas" align=center> </canvas>
<span class="text">SUBMIT</span>
</button>
</a>
</div>

Resizing a <canvas> Element

I have the following canvas. I'm trying to make it smaller using the width and height attributes, but it doesn't work. This is my code:
<!DOCTYPE HTML>
<html>
<head>
<style>
body {
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<canvas id="canvas" width="200" height="50"></canvas>
<script>
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
w = a.width = window.innerWidth,
h = a.height = window.innerHeight,
area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = .01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - .05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if(this.r <= .05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0,0,w,h);
for(var i = 0; i < particles.length; i++) {
if(particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if(particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for(var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max)?max:1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
</script>
</body>
</html>

Pay more attention here:
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
w = a.width = window.innerWidth,
h = a.height = window.innerHeight,
area = w * h,
As you can see, w is the width of the window and h is the height of the window. Try to edit w and h variable with custom values and tell me if it worked ;)
EDIT:
Simply replace h and w with this in your script tag:
a.style.width = '500px'; //random value, insert custom here
a.style.height = '500px';