Skeleton boilerplate code supports the responsive design of the site.
Audio is provided by responsivevoice.org
English and Thai text is displayed using fonts from Google Web Fonts which allows fonts to be loaded dynamically from the Internet meaning the developer doesn't need to worry about which fonts are installed on the user's computer and ensures that the website looks essentially the same on all platforms.
IPA text is displayed using a customised version of the Andika font which is released under the SIL Open Font License.
The Thai language passages in the Speed Test and Typing Practice are used with permission from thai-language.com.