Importing 1.3.9 template into 1.5.5

[mc12345678]

Mind you "working" is not necessarily the litmus test as even some template modifications were made back in ZC 1.5.1 to simply present the data more consistently/securely.

There also was a change in template handling of ezpages, as well as the product link on product pages, and some other modifications. One that you mentioned was the general use of $_POST versus $_GET. Besides the size limitation of $_GET calls, it also helps to transport the information more securely (ie. Not being in the url.)
As for remaining custom build parts, if you have been using the ZC functions such as zen_draw_form then great, otherwise you will need to update such "blocks" to incorporate the securitytoken.

Again, comparison of the old template_default related file(s) to the same file for current operations should help to identify what other differences may be of concern/interest.

Overall templatewise, yeah folder structure is pretty much the same, new features have been added, security strengthened, additional ways/methods to integrate code without modifying the file(s) (see notifier/observer related discussion), updated internal operations to modernize the code as permitted within the software's constraints though interesting to see that ZC 1.5.5 has been able to continue supporting earlier versions of PHP, etc... some of these things may require referencing different functions or the same but with different parameters now as compared to before...

[schoolboy]

I see how CSS is even more split up in Responsive but I really don't need that level of granularity. Sniffer and Mobile_Detect seem to be going overboard. I respect the attempt to nail down all known devices but it looks like another maintenance hassle. I do like the basic Responsive code though. It's impressive. I doubt I'll ever use it.

My greatest challenge is the client is so married to their big, static-width, grandiose and lavishly decorated desktop design that going responsive is just gonna break their hearts. You can see it at custom sticker makers dot com.

What your client "likes and wants" are largely irrelevant. You need to tell them this - and be frank about it. What matters is HOW the web is now being used by online shoppers, and HOW the major search engines are evaluating the User Experience.

Clunky, overweight and "fixed-width" websites are 100% redundant. Well over 50% of internet users now access and interact with websites on mobile devices (smartphones to tablets), and in this regard, responsiveness is absolutely critical. The challenge here is that responsive flexibility is device-influenced - hence the heavyweight CSS and JS coding that governs it.

Two major evaluation criteria now critical for optimal search engine performance are:
1. Mobile Responsiveness
2. Pagespeed

Low scores on either will get severe penalties from search engines, never mind the frustrations experienced by the majority of web shoppers who now work on small devices.

If your client fails to see how things are evolving on the WWW, then they are putting their business at risk.