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var canvas = document.getElementById('tutorial');
// Make sure we don't execute when canvas isn't supported
if (canvas.getContext){
// use getContext to use the canvas for drawing
var ctx = canvas.getContext('2d');
// Draw shapes
for (i=0;i<4;i++){
for(j=0;j<3;j++){
ctx.beginPath();
var x = 25+j*50; // x coordinate
var y = 25+i*50; // y coordinate
var radius = 20; // Arc radius
var startAngle = 0; // Starting point on circle
var endAngle = Math.PI+(Math.PI*j)/2; // End point on circle
var clockwise = i%2==0 ? false : true; // clockwise or anticlockwise
ctx.arc(x,y,radius,startAngle,endAngle, clockwise);
if (i>1){
ctx.fill();
} else {
ctx.stroke();
}
}
}
}
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