This heading explains the working of tasks or instructions that you have just completed.

You will also find some other learning aids in the book, including:

These are short multiple-choice questions intended to help you test your own understanding.

These practical challenges give you ideas for experimenting with what you have learned.

You will also find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "Next, we'll add a drawText() method to the Canvas2D object."

A block of code is set as follows:

this.drawText = function(text, point, fill)
{
    if (fill)
    {
        context.fillText(text, point.x, point.y);
    }
    else
    {
        context.strokeText(text, point.x, point.y);
    }
};

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

switch (action.tool)
{
    // code not shown...
    case "text":
        canvas2d.drawText(action.text, action.points[0],
            action.fill);
        break;
}

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "When the Save button is clicked, it will get the data URL and then open it."