<script>
            (function() {

                // detect if IE : from http://stackoverflow.com/a/16657946
                var ie = (function(){
                    var undef,rv = -1; // Return value assumes failure.
                    var ua = window.navigator.userAgent;
                    var msie = ua.indexOf('MSIE ');
                    var trident = ua.indexOf('Trident/');

                    if (msie > 0) {
                        // IE 10 or older => return version number
                        rv = parseInt(ua.substring(msie + 5, ua.indexOf('.', msie)), 10);
                    } else if (trident > 0) {
                        // IE 11 (or newer) => return version number
                        var rvNum = ua.indexOf('rv:');
                        rv = parseInt(ua.substring(rvNum + 3, ua.indexOf('.', rvNum)), 10);
                    }

                    return ((rv > -1) ? rv : undef);
                }());


                // disable/enable scroll (mousewheel and keys) from http://stackoverflow.com/a/4770179
                // left: 37, up: 38, right: 39, down: 40,
                // spacebar: 32, pageup: 33, pagedown: 34, end: 35, home: 36
                var keys = [32, 37, 38, 39, 40], wheelIter = 0;

                function preventDefault(e) {
                    e = e || window.event;
                    if (e.preventDefault)
                    e.preventDefault();
                    e.returnValue = false;
                }

                function keydown(e) {
                    for (var i = keys.length; i--;) {
                        if (e.keyCode === keys[i]) {
                            preventDefault(e);
                            return;
                        }
                    }
                }

                function touchmove(e) {
                    preventDefault(e);
                }

                function wheel(e) {
                    // for IE
                    //if( ie ) {
                        //preventDefault(e);
                    //}
                }

                function disable_scroll() {
                    window.onmousewheel = document.onmousewheel = wheel;
                    document.onkeydown = keydown;
                    document.body.ontouchmove = touchmove;
                }

                function enable_scroll() {
                    window.onmousewheel = document.onmousewheel = document.onkeydown = document.body.ontouchmove = null;
                }

                var docElem = window.document.documentElement,
                    scrollVal,
                    isRevealed,
                    noscroll,
                    isAnimating,
                    container = document.getElementById( 'container' ),
                    trigger = container.querySelector( 'button.trigger' );

                function scrollY() {
                    return window.pageYOffset || docElem.scrollTop;
                }

                function scrollPage() {
                    scrollVal = scrollY();

                    if( noscroll && !ie ) {
                        if( scrollVal < 0 ) return false;
                        // keep it that way
                        window.scrollTo( 0, 0 );
                    }

                    if( classie.has( container, 'notrans' ) ) {
                        classie.remove( container, 'notrans' );
                        return false;
                    }

                    if( isAnimating ) {
                        return false;
                    }

                    if( scrollVal <= 0 && isRevealed ) {
                        toggle(0);
                    }
                    else if( scrollVal > 0 && !isRevealed ){
                        toggle(1);
                    }
                }

                function toggle( reveal ) {
                    isAnimating = true;

                    if( reveal ) {
                        classie.add( container, 'modify' );
                    }
                    else {
                        noscroll = true;
                        disable_scroll();
                        classie.remove( container, 'modify' );
                    }

                    // simulating the end of the transition:
                    setTimeout( function() {
                        isRevealed = !isRevealed;
                        isAnimating = false;
                        if( reveal ) {
                            noscroll = false;
                            enable_scroll();
                        }
                    }, 600 );
                }

                // refreshing the page...
                var pageScroll = scrollY();
                noscroll = pageScroll === 0;

                disable_scroll();

                if( pageScroll ) {
                    isRevealed = true;
                    classie.add( container, 'notrans' );
                    classie.add( container, 'modify' );
                }

                window.addEventListener( 'scroll', scrollPage );
                trigger.addEventListener( 'click', function() { toggle( 'reveal' ); } );
            })();
        </script>