The app is based on the already existing services (Instagram, Tumblr and Wordpress). It extracts the posts that are tagged with a specific hashtag from each of those 3 systems (e.g. #divinatorium or #korpus) and creates a set of content items from them.
The frontend user is then proposed to pick certain content items from the set (e.g. by clicking 3 times on an animated html5 square that shows all the images tagged with #divinatorium or #korpus in a quick succession). Or by choosing 1 of 22 hidden cards. Each selected image is then shown as a post extracted from Wordpress / Tumblr / Instagram with the text that goes with it.
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Important: the initial project description contains frontend mockup only.
Backend would have settings (which services to extract from and respective logins).
It should be possible to later extend this app with a Wordpress plugin that would automatically connect it to WP through its API.
IMPORTANT UPDATE TO THE TASK:
We will create this app as a Wordpress theme / plugin directly.
This will resolve later issues with user / login issues and will make it unnecessary to write separate blocks to import content (we will simply import everything into Wordpress)
So your only task will be to build frontend functionality that will run as a theme / plugin on top of Wordpress.
User interaction will stay the same, as shown above on https://marvelapp.com/2ah248h