HTML5 Canvas Crazy Snake

HTML Code:


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <canvas id="canvas" height="300px" width="600px" ></canvas>
    <script>
    window.requestAnimFrame = (function(callback){
    return window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function(callback){
        window.setTimeout(callback, 1000 / 60);
    };
})();
 
function getRandTheta(){
    return Math.random() * 2 * Math.PI;
}
 
function updateSnake(canvas, snake){
    var maxVariance = 0.2;
    var snakeSpeed = 200; //px / s
    var segmentsPerSecond = snakeSpeed / snake.segmentLength;
    var segments = snake.segments;
    var date = new Date();
    var time = date.getTime();
    var timeDiff = (time - snake.lastUpdateTime);
    if (timeDiff > 1000 / segmentsPerSecond) {
        var head = segments[segments.length - 1];
        var neck = segments[segments.length - 2];
 
        var direction = snake.direction;
        var newHeadX = head.x + direction.x * snake.segmentLength;
        var newHeadY = head.y + direction.y * snake.segmentLength;
 
        // change direction if collision occurs
        if (newHeadX > canvas.width || newHeadX < 0) {
            direction.x *= -1;
        }
        if (newHeadY > canvas.height || newHeadY < 0) {
            direction.y *= -1;
        }
 
        // add new segment
        segments.push({
            x: newHeadX,
            y: newHeadY
        });
 
        if (segments.length > snake.numSegments) {
            segments.shift();
        }
 
        var variance = ((maxVariance / 2) - Math.random() * maxVariance);
 
        direction.x += variance;
        direction.y -= variance;
 
        // update direction vector
        if (direction.x > 1) {
            direction.x = 1;
        }
        if (direction.x < -1) {
            direction.x = -1;
        }
 
        // dampering - try to keep direction vectors around -0.5 and +0.5
        direction.x *= Math.abs(direction.x) > 0.5 ? (1 - 0.01) : (1 + 0.01);
        direction.y *= Math.abs(direction.y) > 0.5 ? (1 - 0.01) : (1 + 0.01);
 
        snake.lastUpdateTime = time;
    }
}
 
function animate(canvas, snake){
    var context = canvas.getContext("2d");
 
    // update
    updateSnake(canvas, snake);
 
    // clear
    context.clearRect(0, 0, canvas.width, canvas.height);
 
    // draw
    drawSnake(context, snake);
 
    // request new frame
    requestAnimFrame(function(){
        animate(canvas, snake);
    });
}
 
function drawSnake(context, snake){
    var segments = snake.segments;
    var tail = segments[0];
    context.beginPath();
    context.moveTo(tail.x, tail.y);
 
    for (var n = 1; n < segments.length; n++) {
        var segment = segments[n];
        context.lineTo(segment.x, segment.y);
    }
 
    context.lineWidth = 10;
    context.lineCap = "round";
    context.lineJoin = "round";
    context.strokeStyle = "green";
    context.stroke();
}
 
window.onload = function(){
    var canvas = document.getElementById("canvas");
    var segmentLength = 2; // px
    var headX = canvas.width / 2;
    var headY = canvas.height / 2;
 
    snake = {
        segmentLength: 2,
        lastUpdateTime: 0,
        numSegments: 50,
        // moving to the right
        direction: {
            x: 1,
            y: 0
        },
        segments: [{
            // tail
            x: headX + segmentLength,
            y: headY
        }, {
            // head
            x: headX,
            y: headY
        }]
    };
 
    animate(canvas, snake);
};    
        
        
    </script>
</body>
</html>

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<!DOCTYPE html>

<head>

<title>Document</title>

</head>

<body>

window.requestAnimFrame = (function(callback){

return window.requestAnimationFrame ||

window.webkitRequestAnimationFrame ||

window.mozRequestAnimationFrame ||

window.oRequestAnimationFrame ||

window.msRequestAnimationFrame ||

function(callback){

window.setTimeout(callback, 1000 / 60);

};

})();

function getRandTheta(){

return Math.random() * 2 * Math.PI;

}

function updateSnake(canvas, snake){

var maxVariance = 0.2;

var snakeSpeed = 200; //px / s

var segmentsPerSecond = snakeSpeed / snake.segmentLength;

var segments = snake.segments;

var date = new Date();

var time = date.getTime();

var timeDiff = (time - snake.lastUpdateTime);

if (timeDiff > 1000 / segmentsPerSecond) {

var head = segments[segments.length - 1];

var neck = segments[segments.length - 2];

var direction = snake.direction;

var newHeadX = head.x + direction.x * snake.segmentLength;

var newHeadY = head.y + direction.y * snake.segmentLength;

// change direction if collision occurs

if (newHeadX > canvas.width || newHeadX < 0) {

direction.x *= -1;

}

if (newHeadY > canvas.height || newHeadY < 0) {

direction.y *= -1;

}

// add new segment

segments.push({

x: newHeadX,

y: newHeadY

});

if (segments.length > snake.numSegments) {

segments.shift();

}

var variance = ((maxVariance / 2) - Math.random() * maxVariance);

direction.x += variance;

direction.y -= variance;

// update direction vector

if (direction.x > 1) {

direction.x = 1;

}

if (direction.x < -1) {

direction.x = -1;

}

// dampering - try to keep direction vectors around -0.5 and +0.5

direction.x *= Math.abs(direction.x) > 0.5 ? (1 - 0.01) : (1 + 0.01);

direction.y *= Math.abs(direction.y) > 0.5 ? (1 - 0.01) : (1 + 0.01);

snake.lastUpdateTime = time;

}

function animate(canvas, snake){

var context = canvas.getContext("2d");

// update

updateSnake(canvas, snake);

// clear

context.clearRect(0, 0, canvas.width, canvas.height);

// draw

drawSnake(context, snake);

// request new frame

requestAnimFrame(function(){

animate(canvas, snake);

});

}

function drawSnake(context, snake){

var segments = snake.segments;

var tail = segments[0];

context.beginPath();

context.moveTo(tail.x, tail.y);

for (var n = 1; n < segments.length; n++) {

var segment = segments[n];

context.lineTo(segment.x, segment.y);

}

context.lineWidth = 10;

context.lineCap = "round";

context.lineJoin = "round";

context.strokeStyle = "green";

context.stroke();

}

window.onload = function(){

var canvas = document.getElementById("canvas");

var segmentLength = 2; // px

var headX = canvas.width / 2;

var headY = canvas.height / 2;

snake = {

segmentLength: 2,

lastUpdateTime: 0,

numSegments: 50,

// moving to the right

direction: {

x: 1,

y: 0

segments: [{

// tail

x: headX + segmentLength,

y: headY

}, {

// head

x: headX,

y: headY

}]

};

animate(canvas, snake);

};

</script>

</body>

</html>

HTML5 Canvas Crazy Snake2 min read

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