HTML Site Gallery
Prev ImageNext Image
Submit Site
Cut The Rope
Site Pinning


Cut the Rope is an immediate favorite for anyone who plays it. It's as fun as it is adorable. So we had an idea: let's make this great game available to an even bigger audience by offering it on the web using the power of HTML5.

To do this, Microsoft's Internet Explorer team partnered with ZeptoLab (the creators of the game) and the specialists at Pixel Lab to bring Cut the Rope to life in a browser. The end result is an authentic translation of the game for the web, showcasing some of the best that HTML5 has to offer: canvas-rendered graphics, browser-based audio and video, CSS3 styling and the personality of WOFF fonts.

We think that the HTML5 version makes the web more fun and it demonstrates the advances in standards support made in the latest version of Internet Explorer. With that in mind, we want to share some of the cool "behind the scenes" technical details used on this project to help you build your own HTML5 sites and ultimately get ready for the Windows 8 Store!

HTML5 usage:

A great thing about HTML5 is that you don't need to learn a new language to unlock the power of this new technology. If you know and understand JavaScript, you already have access to all that a modern browser can do. You could even create your own game like this!

In bringing Cut the Rope to a new platform, we wanted to ensure we preserved the unique physics, motion, and personality of the experience. So early on we decided to approach this game as a "port" from the native iOS version (rather than a rewrite). We kicked off the project with an extensive investigation of the original Objective-C codebase. Turns out it's a big and complex game. The native iOS version consists of about 15,000 lines of code (excluding libraries)! The most complex parts of the codebase are the physics, animation, and drawing engines. They're complex on their own, but made even more so by the fact that all three are tightly connected and highly optimized.

In the past, JavaScript had a reputation of being a slow language. Frankly, that reputation was initially valid. Older JavaScript engines were designed for simple "scripting" kinds of tasks (hence the name). Today, however, JavaScript engines have been highly optimized. With features like just-in-time compilation, JavaScript now can execute at near native speeds.

Beyond that, we know that coding for JavaScript is different from - and requires a different kind of mindset than - coding in a compiled language. As we ported the game from Objective-C, we knew we would need to embrace the task of making these sorts of changes and optimizations.

One obvious example was the lack of structs in JavaScript. Structs are lightweight aggregations of related properties. It's easy to use a JavaScript object to hold a set of properties, but there are important differences between that approach and a proper struct. The first difference is that structs get copied whenever they're assigned to a variable or passed to a function. So, a function written in a compiled language like Objective-C can modify a struct passed as a parameter without affecting the value in the caller. Even within a function, assignment of a struct to a different variable will copy the values. JavaScript objects, on the other hand, are passed by reference. So when a function modifies an object parameter, the changes will be visible to the caller.

An easy way to mimic the nature of structs is to create copies of JavaScript objects for assignment or parameter passing. In native languages there is typically very little overhead to using structs. Creating an object in JavaScript is much more expensive, so we had to be very careful to minimize the number of allocations. Particularly on assignments, whenever possible we tried to copy individual properties rather than creating entirely new object instances.

Another example is the object oriented nature of the Objective-C codebase. In lieu of traditional object-based inheritance, JavaScript offers prototypical inheritance, inheritance based on the Prototype property. This is a highly simplified form of object inheritance that really isn't compatible with a traditional object oriented language like Objective-C. Fortunately, there are a variety of class libraries that can help you write object-oriented programming (OOP) style code for JavaScript; we made use of a very simple one that was written by John Ressig (of jQuery fame). (Note that ECMAScript5, the specification for the newest version of JavaScript, also includes some support for classes but we opted not to use it in this port due to our lack of familiarity with that version of the language coupled with our aggressive development schedule).

In addition to porting from Objective-C to JavaScript, we also needed to port our graphics code from OpenGL to the HTML5 Canvas API. Overall, this went really smoothly. Canvas is an amazingly fast rendering surface, especially in a browser where that API is hardware accelerated (like Internet Explorer 9).

Check out the full Behind the Scenes Story right here

Technology Used:


HTML5 Browser Optimized for:


Device Optimized for:



  • Web Development Newsletter Signup

    Invalid email
    You have successfuly registered to our newsletter.
Thanks for your registration, follow us on our social networks to keep up-to-date