Emanuele Feronato

var game;
// colors is actually the array of level pages
var colors = ["0xffffff","0xff0000","0x00ff00","0x0000ff","0xffff00"];
// columns of thumbnails in each page
var columns = 3;
// rows of thumbnails in each page
var rows = 4;
// thumbnail width, in pixels
var thumbWidth = 60;
// thumbnail height, in pizels
var thumbHeight = 60;
// empty space between two thumbnails, in pixels
var spacing = 20;
window.onload = function() {
 // creating a 320x480 pixels game and executing PlayGame state 	
	game = new Phaser.Game(320, 480, Phaser.AUTO, "");
 game.state.add("PlayGame", playGame);
 game.state.start("PlayGame");
}
var playGame = function(game){};
playGame.prototype = {
 preload: function(){
 // level thumbnail 
 game.load.image("levelthumb", "levelthumb.png");
 // level pages at the bottom
 game.load.image("levelpages", "levelpages.png");
 // transparent background used to scroll
 game.load.image("transp", "transp.png");
 },
 create: function(){ 
 // setting game background color
 game.stage.backgroundColor = "#222222"; 
 // just a text placed on the top of the stage to show level page
 this.pageText = game.add.text(game.width / 2, 16, "Swipe to select level page (1 / " + colors.length + ")", {font: "18px Arial", fill: "#ffffff"})
 this.pageText.anchor.set(0.5);
 // the tiled transparent sprite, covering the entire scrollable area which width is (number of pages) * (game width)
 this.scrollingMap = game.add.tileSprite(0, 0, colors.length * game.width, game.height, "transp");
 // this is how we tell Phaser the sprite can receive inputs
 this.scrollingMap.inputEnabled = true;
 // the sprite can be dragged
 this.scrollingMap.input.enableDrag(false);
 // the sprite can't be dragged vertically
 this.scrollingMap.input.allowVerticalDrag = false;
 // this is the bounding box which defines dragging limits
 this.scrollingMap.input.boundsRect = new Phaser.Rectangle(game.width - this.scrollingMap.width, game.height - this.scrollingMap.height, this.scrollingMap.width * 2 - game.width, this.scrollingMap.height * 2 - game.height);
 // we start at page zero, that is the first page
 this.currentPage = 0;
 // this will be the array of page thumbnails
 this.pageSelectors = [];
 // determining row length according to thumbnail width, spacing and number of columns
 var rowLength = thumbWidth * columns + spacing * (columns - 1);
 // left margin is set to every row is centered in the stage
 var leftMargin = (game.width - rowLength) / 2;
 // same concept applies to column height and top margin
 var colHeight = thumbHeight * rows + spacing * (rows - 1);
 var topMargin = (game.height - colHeight) / 2;
 // looping through all pages
 for(var k = 0; k < colors.length; k++){
 // looping through all columns
 for(var i = 0; i < columns; i++){
 // looping through all rows
 for(var j = 0; j < rows; j++){
 // adding level thumbnail
 var thumb = game.add.image(k * game.width + leftMargin + i * (thumbWidth + spacing), topMargin + j * (thumbHeight + spacing), "levelthumb");
 // setting tint color according to page cumber
 thumb.tint = colors[k];
 // each level has a number...
 thumb.levelNumber = k * (rows * columns) + j * columns + i;
 // which we are going to write inside the thumbnail
 var levelText = game.add.text(0, 0, thumb.levelNumber, {font: "24px Arial", fill: "#000000"})
 // level number is added as a child of level thumbnail
 thumb.addChild(levelText);
 // level thumbnail is added as a child of scrolling map
 this.scrollingMap.addChild(thumb);
 }
 }
 // now it's time to place page thumbnail selectors, in a way they are centered on the stage
 this.pageSelectors[k] = game.add.button(game.width / 2 + (k - Math.floor(colors.length / 2) + 0.5 * (1 - colors.length % 2)) * 40, game.height - 40, "levelpages", function(e){
 // each page thumbnail once clicked will scroll the map by "difference" pages
 var difference = e.pageIndex - this.currentPage;
 // changePage will handle scrolling
 this.changePage(difference);
 }, this);
 // each page selector is anchored on its center point
 this.pageSelectors[k] .anchor.set(0.5);
 // each page selector has a page index according to the page it refers to
 this.pageSelectors[k].pageIndex = k;
 // adding a tint color so we can see we will move to "red" levels if we click or "red" page, to "green" levels if we click on "green" page and so on
 this.pageSelectors[k].tint = colors[k];
 // this is just to highlight current page, making it bigger (actually we are making other pages smaller)
 if(k == this.currentPage){
 this.pageSelectors[k].height = 30;
 }
 else{
 this.pageSelectors[k].height = 15;
 }
 }
 // when we start dragging, we just save horizontal map position
 this.scrollingMap.events.onDragStart.add(function(sprite, pointer){
 this.scrollingMap.startPosition = this.scrollingMap.x;
 }, this);
 // the core of the script is when we STOP dragging
 this.scrollingMap.events.onDragStop.add(function(sprite, pointer){
 // if there wasn't any scroll, we can say it wasn't a drag so the player clicked a level
 if(this.scrollingMap.startPosition == this.scrollingMap.x){
 // now we just have to check for all bounding boxes to see which level thumbnail has been clicked
 // sadly, we can't use buttons or they won't allow to detect scrolling
 for(i = 0; i < this.scrollingMap.children.length; i++){
 var bounds = this.scrollingMap.children[i].getBounds(); 
 if(bounds.contains(pointer.x, pointer.y)){
 alert("Play level " + this.scrollingMap.children[i].levelNumber);
 break; 
 } 
 }
 }
 else{
 // we define 1/8 of the width of the page as the minimum amount of pixels scrolled to say the player
 // wanted to swipe the page
 if(this.scrollingMap.startPosition - this.scrollingMap.x > game.width / 8){
 this.changePage(1);
 }
 else{
 if(this.scrollingMap.startPosition - this.scrollingMap.x < - game.width / 8){
 this.changePage(-1);
 }
 else{
 this.changePage(0);
 }
 }
 }
 }, this);
 },
 changePage: function(page){
 // here we move the scrolling map according to selected page
 this.currentPage += page;
 for(var k = 0; k < colors.length; k++){
 if(k == this.currentPage){
 this.pageSelectors[k].height = 30;
 }
 else{
 this.pageSelectors[k].height = 15; 
 }
 }
 this.pageText.text = "Swipe to select level page (" + (this.currentPage + 1).toString() + " / " + colors.length + ")"; 
 var tween = game.add.tween(this.scrollingMap).to({
 x: this.currentPage * -game.width 
 }, 300, Phaser.Easing.Cubic.Out, true);
 }
}

Never miss an update! Subscribe, and I will bother you by email only when a new game or full source code comes out.