The toy is quite demanding on browser performance. Experiments show that it goes best in Chrome 10 and IE9.
For rendering animations, sprites are used and, as suggested in the comments, easeljs.com library. For example, the Kracken storyboard looks like this:
To insert fonts, use font-face and the www.fontsquirrel.com service to generate the desired set of files and code.
For storage of the account is used Local Storage.
When developing the game, I had to tinker with the sound, especially when it was necessary to dynamically play several files at the same time.
The graphics were developed in Adobe Illustrator, animated in Flash Pro and then converted using a special AIR tool on the AIR swf file into a sprite.