excellent post.

can i make a (hopefully useful) comment about programming style - something that someone shared with me a long time ago when reading my code that i have found to be very valuable over the years?

it can be incredibly beneficial (for readability, catching logic errors, etc.) to "exit early" from "if" statements. meaning, if you find that you're nesting "ifs" more than a couple of levels deep, the code may be a candidate for flattening.

so - your handleClick function could be rewritten (with stuff removed) as:

    var handleClick = function( id )
    {
        if ( gameOver ) return;
        if ( ctrlIsPressed )
        {
            // do stuff...
            return;
        }
        if ( cell.opened || cell.flagged ) return;
        if ( cell.mined )
        {
            // do stuff...
            return;
        }
        // else do stuff...
        if ( cell.neighborMineCount > 0 )
        {
            // ...
            return;
        }

        // else do final stuff...
    }

i may have missed something, but hopefully you get the point. this simple refactoring reduced the depth of the if statements from ~5 to 1. ...many of the other functions could be flattened just like this.

...and how do you know when something can be flattened?

if there is no code after the if statement and the end of the function - just swap the logic and return early.

e.g., this:

    var handleClick = function( id )
    {
        if ( !gameOver )
        {
            // ...lots of code and if statements...
        }
        // ...but no code after the block before returning from the function...
    }

...turns into this:

    var handleClick = function( id )
    {
        if ( gameOver ) return; // NOTE: logic check change...
        // ...do the stuff in the block here...
    }

...and this is also a great pattern for checking input variables (and returning or throwing an exception) at the top of the function, ensuring that the code following it has valid input parameters.

since you're sharing your coding projects on your blog (which are excellent) - hopefully you can share this tidbit about coding style with your readers and they'd find it as useful as i have.