Action Script is the scripting language used with Macromedia (now Adobe) Flash to create interactive shockwave files for display in a web browser. it is fun to use but has its problems for beginners. Here is a simple shockwave example with a few faults.
You need Falsh software to build shockwave files. Newer versions of Flash are expensive but you can sometimes pick up older versions on the internet. Your other problem is that newer versions of the software are not backwards compatible. Likewise browsers. This was built with Flash version CS4 but the shockwave files it creates are already not compatible with Internet Explorer.
Here are a few simple interactive games built using Flash CS4 (coding script is Actionscript). In each case there is a link to the actual game running in an html web page and to a pdf file of the coding used to build the game. The graphics have also been generated using Adobe Flash CS4. If your browser has trouble displaying a game refresh its screen.
Flash Games