GocikaCMS is a very simple, flat file CMS that is SEO friendly and responsive - built in PHP (minimum requirements are PHP 5). It takes a few seconds to configure (just one config file). It works on all major browsers including mobile versions. It is absolutely mobile first.
The biggest difference between gocikaCMS and other flat file, responsive content management platforms is that its very small, takes seconds to start. It uses purecss.io and parsedown.org to produce wonderfully lightweight web pages. You use markdown to write the content and it outputs in bloat-free, fast, html.
You can create smart looking micro sites with ease, but if you want to extend them into full sites, then a bit of fiddling with HTML, maybe some PHP and you can have fully-fledged websites too - very SEO friendly.
If you want to make simple static content sites in very quick time, then gocikaCMS is the CMS for you. It is perfect for creating hobby sites, or micro sites, and with the templates included, you can produce very smart, content-rich sites in no time.
Gocika version 1.01, the latest release, is now under 2k in size (although I'm constantly looking to make this smaller, but does the same job as other CMS systems that are at least 10 times the size.