Building a responsive floating button with javascript and css

We have a button that we need to load on external websites, that can be loaded by adding a line or two to any website. The button will be either red or blue, as decided by our server, on each load. The button should be loaded responsively, and be fixed/floating above all other content on the page. Mobile: Almost full width (90%) Tablet: 50% width Desktop: About 450px wide Attached is a sample of how it should look on mobile/tablet/web. Attached is a PSD with both the blue and red buttons. The finished code that we can use to add the buttons to websites should be something like: <script type="text/javascript"> var chash = ABC123; var cdesc = "SOME DESCRIPTIVE NAME"; </script> <script type="text/javascript" src="//[login to view URL]"></script> Then the script should add a button to the website which will act as a link with a link something like this: <a href="//somedomain.com/buttonclick/ABC123/SOME+DESCRIPTIVE+NAME?utmsource=button&utmcampaign=red&referrer=[login to view URL]" target="_blank" rel="nofollow"></a> Where [login to view URL] is the referring websites domain. the hash and description name are set on each website and should determine what url the button directs too. The buttons should also have a close button to hide the button. if this close button is clicked, an AJAX request should be made to the server, so we can remember to not show the button on future pageviews for that user. The server will dynamically generate the javascript code for the button at //[login to view URL] which will determine whether to use the red or blue button, and will therefore give the correct url for the correct button (image/css) etc.. I need someone to create the javascript/css/image files which can these buttons and display in the right place floating on both web/tablet/mobile. This button should be coded in simple javascript and not need jquery or any other libraries. The button should work on all browsers and devices.