It is simple really. I have just created an example for you:
life_system.zip (101 KB)
In case you are using the Mac version, I could be wrong but I guess it able to export only HTML5, if that is the case and you are preview the project in HTML5, make sure you run a hard refresh between each preview because the web browsers likes to use stored version of webpages to speed loading time so when you run preview, your browser may decide to load the previous version instead of the new version and makes you think it doesn’t work what you have just done, but really it is your browser. So do a hard refresh in your browser to make sure the actual changes are loaded.